Geo 101
Laccolith
A laccolith is parallel to the layering of the rocks into which it intrudes, like a sill, but forces the layers of rock above it to bend, forming a dome.
Molecule
A molecule is the smallest unit that has the distinctive chemical properties of a compound.
Phaneritic
Coarse-grained, intrusive igneous rock texture with large crystals easily seen by the naked eye is called phaneritic.
Dike
Dikes are tabular, sheet-like (thin but laterally extensive) body of igneous rock that cuts across the layering of the rock into which it intrudes.
Evaporation
Evaporation is the exchange of water from a liquid to a vapor.
Sedimentary Rock
Formed from deposits of sediment.
Aa
High viscosity, low temp
Silicate Tetrahedra
Olivine and garnet are examples of silicate minerals in which the crystal structures consist of isolated silicate tetrahedra that are not linked in any way.
Which of these minerals has the greatest hardness?
Olivine.
At a passive continental margin the primary geologic process occuring is
Sedimentation.
Stock
Stocks are small irregular-shaped intrusions no larger than 10 km in maximum dimension.
Isolated System
The boundary completely prevents the exchange of either matter or energy.
Continental Shelf
The continental shelf is the low-lying portion of the continent flooded by shallow seas.
Hydrosphere
The hydrosphere is water in all its forms. Different surface temperatures and pressures allow water to exist on Earth in all three states: solid, liquid, and gas. Most of the water is located in the oceans (97.5%). Glaciers (1.8%), groundwater (0.63%), streams and lakes (0.01%) and the atmosphere (0.001%) hold the rest.
Phenocryst
The isolated large grains are phenocrysts.
Plates and Plate Tectonics
The theory of plate tectonics states that Earth's outermost layer (crust) is broken into a number of large and small plates. The plates move relative to one another because they rest on top of hotter, more mobile material. The theory of plate tectonics ties the observations of continental drift, seafloor spreading, and subduction together while also explaining related geologic phenomena (such as volcanoes and earthquakes). The earth's lithosphere is broken into about a dozen major pieces and numerous smaller fragments called plates. The lithospheric plates float on the denser but weaker asthenosphere and move in different directions and speeds relative to one another.
Periodic Table
There are 93 naturally occurring elements (additional elements have been created in the laboratory) arranged by atomic number in the periodic table.
Transpiration
Transpiration is the release of water into the atmosphere by plants and animal cells.
Pangaea
Wegner stated that the continents were once joined as one land mass he called Pangaea which broke apart and the fragments (today's continents) slowly drifted to their present positions.
Continental Rifting and Rift Valley
Where a continent is being pulled apart a new divergent boundary called a continental rift valley is created. The East African Rift Valley is an example of a continental rift. Continental rift valleys represent the earliest stage in the development of a new ocean basin as a single continental plate splits into two fragments as new oceanic crust grows between them. The process begins when crust is heated by rising magma from the mantle, causing uplift of a broad area As rising magma continues to push the crust aside, the uplift collapses to form a rift valley New oceanic crust is created as the rift spreads. The area is flooded to form a narrow sea such as the Red Sea The narrow sea may grow to become a new ocean basin with a mid-ocean ridge and seafloor spreading center.
Sulphide
contain sulfur atoms
Batholith
A batholith is the largest kind of pluton. It is an intrusive igneous body of irregular shape that cuts across the layering or other fabric of the rock into which it intrudes. The magma forming batholiths intrudes upward from its source deep in the continental crust.
Peridotite-Komatite
A coarse-grained igneous rock in which olivine is the most abundant, and sometimes the only, mineral present is called peridotite. Peridotite is abundant in the mantle but exposures at the surface are relatively rare. The extrusive equivalent of peridotite is komatite and is even rarer. All known komatites are older than two billion years, indicating that the processes responsible for eruption of ultramafic magmas at the surface no longer occur on Earth.
Granite-Rhyolite
A felsic (also called rhyolitic or granitic) igneous rock is composed mostly of light colored minerals and is called granite if it is intrusive and rhyolite if it is extrusive. The main minerals in felsic igneous rocks are quartz and potassium feldspar. Mica (muscovite) and amphibole (hornblende) are typically present in small amounts. Granitic rocks are found in the continental crust. Granitic magma forms when continental crust is heated to its melting point. This occurs at convergent plate boundaries where at least one of the plates is composed of continental crust.
Tephra
A fragment of rock ejected during a volcanic eruption is called a pyroclast. Rocks formed from pyroclasts are pyroclastic rocks. Tephra is a collective term for all airborne pyroclasts.
Lahar
A lahar is a mixture of water and rock fragments flowing down the slopes of a volcano and channeled a great distance from the volcano along river valleys. Lahars are sometimes referred to as volcanic mudflows or debris flows. As a lahar rushes downstream, its size, speed, and the amount of water and rock debris it carries constantly changes as it erodes and incorporates lose rock, vegetation and other debris, and gains water from melting snow and ice and the river it overruns.
Mineral
A mineral is a naturally occurring, inorganic solid that has a defined chemical composition and crystalline structure. The composition of a mineral is the chemical elements that make up the mineral and their exact proportions.
Describe the physical properties that you would use to distinguish A) halite from calcite and B) galena from graphite.
A) Halite is generally more of a reddish brown color then calcite. Calcite will generally be a little bit harder, although this may be hard to distinguish. Halite is formed at right angles in regards to their cleavage and fractures. B) Graphite may be slightly more black in color and a little bit duller than galena. Galena will be a little bit harder than graphite. Galena will be in three right gales forming cubes while graphite is just in one direction in regards to their cleavage and fractures. Graphite will also be flakey compared to Galena.
Aa
Aa: lower temperature, higher viscosity, a blocky surface texture
Accreted Terrane
Accreted terranes are small pieces of crust too buoyant to be subducted that are carried along by oceanic plates and added to the edge of a continent. Accreted terranes may include old volcanic island arcs, small pieces of continental crust called micro continents, or margins of continents sliced off by transform faults. Accreted terranes can be rafted great distances by plate motions and get added to the edge of continent as the oceanic crust is subducted. The entire west coast of North America is complex jumble of more than 40 accreted terranes added to North America by 200 million years of oceanic subduction in this location. Ocean sediments and anything else too light to subduct such as a volcanic island arc or fragment of continental crust is scraped off and added to edge of continent as accreted terranes.
Contrast the processes and resulting features occurring along active and passive continental margins.
Active continental margins are found where subduction occurs between an oceanic and a continental plate. Active continental margins coincide with plate boundaries. Passive continental margins are found where there is a transition between oceanic and continental crust that is still moving as one plate.
Melting of the mantle in subduction zones is caused by?
Adding water to the magma.
Which of the following plate boundaries is an example of an advanced stage of continental rifting that is developing into a new ocean basin?
African Plate and Arabian Plate
Continental Drift
Alfred Wegener first proposed the hypothesis of continental drift in 1915. According to continental drift the modern continents were once joined as parts of preexisting larger supercontinents. Wegener's hypothesis attempted to explain the jig-saw fit between continents on either side of the Atlantic Ocean. Wegner was also aware that the ages and types of rocks along the African and South American coastlines, as well as the European and North American coastlines, were similar. When the continents were pieced back together, the different rock types lined up nicely. This is illustrated by the distribution of 250 million-year old glacial deposits across the southern continents. The glacial deposits also indicate the direction the ice was moving, and suggest an ice cap centered in South Africa and radiating across the adjoining continents.
Element-Atom-Nucleus-Proton-Neutron-Electron-Atomic Number-Orbital-Shell
All matter, including minerals and rocks, are made of chemical elements. Chemical elements are the most fundamental substances into which matter can be separated by chemical means. The fundamental unit of an element is the atom. Atoms consist of central nucleus made of positively charged protons and electrically neutral neutrons. Negatively charged electrons orbit the nucleus. Each element has a unique number of protons (atomic number). Hydrogen has 1, helium 2, lithium 3, etc. In an atom the number electrons equal the number of protons so the atom is electrically neutral and has no charge. Electrons follow paths called orbitals with different energy levels (shells).
True Polar Wander
Although the magnetic pole does move, it remains within a few degrees of the geographic pole because the magnetic field is generated by the earth's rotation. This is known as true polar wander.
Diorite-Andesite
Andesite is a quartz-poor intermediate igneous rock, the intrusive equivalent is diorite. Andesite and diorite have very little if any quartz and no potassium feldspar. Instead, plagioclase feldspar is the major constituent, and pyroxenes begin to replace the amphiboles. Andesites and diorites are typical of magmatic activity at subduction zones and are produced by melting of water rich subducted oceanic crust; dacites and granodiorites are also typical of subduction zones but their relatively quartz rich composition requires the melting of continental crust as well.
Andesitic
Andesitic magma has an intermediate silica content (55-65%) and intermediate amounts of Fe, Mg, Ca, Na, and K. Andesitic magmas are produced by the partial melting of water rich subducted oceanic crust, which produces a magma richer in silica than the oceanic crust, which is basaltic in composition.
Composite Volcano-Stratovolcano
Andesitic magmas produce tall, conical stratovolanoes (also called composite volcanoes). Composite or stratovolcanoes are characterized by steep sides and conical shapes and are only found at subduction zones because they erupt andesitic magma produce by partial melting of subducted oceanic crust. They are characterized by periods of explosive activity triggered by accumulated, pressurized gases followed by quieter effusion of intermediate viscosity andesitic lava flows as the magma degasses. The resulting volcano is composed of alternating layers of lava flows and pyroclastic deposits, hence the term composite volcano. Pyroclastic deposits consist of material erupted explosively into the air. This may include volcanic ash, tephra, cinders, or bombs.
Isotope
Are atoms with the same number of protons but a different number of neutrons. Isotopes have the same atomic number (hence they are the same element) but a different mass number. For example, the element carbon has three isotopes: carbon-12, carbon-13, and carbon-14. Each has six protons per atom. However, carbon-12 has 6 neutrons, while carbon-13 has seven neutrons and carbon-14 has eight neutrons.
Passive Margin
As a continental rift develops into a new ocean basin, the edges of the continent become a passive continental margin. A passive continental margin is a transition between oceanic and continental crust that does not coincide with an active plate boundary. Instead the plate boundary is at the mid-ocean ridge. Passive continental margins are characterized by cooling and subsidence of the crust as it moves away from rising magma at the mid-ocean ridge and the development of thick sequences of sediments eroded from the continent. The east coast of North America is an example of a passive continental margin.
Bowen's Reaction Series
As magma cools, minerals crystallize in a specific sequence called Bowen's reaction series. The first minerals to crystallize from magma are poor in silica. This makes the remaining (residual) magma richer in silica. As crystallization proceeds the residual magma is enriched in silica, changing the original basaltic magma to andesitic and eventually rhyolitic in composition as silica-poor minerals are crystallized and removed.
Mafic
As temperature increases and melting continues more magic minerals start to melt so the melt is more mafic.
Ion
Atoms are most stable when their outermost electron shells are filled. This can be achieved by donating, accepting, or sharing electrons. By accepting or donating electrons, atoms become electrically charged ions. Ions are atoms with an electric charge resulting from a gain or loss of electrons.
Cation
Atoms containing just one or two electrons in their outermost shell readily donate or lose electrons and become positively charged cations (+). A cation is an atom that has lost an electron and thus has a positive charge.
Anion
Atoms with an almost filled outermost shell accept or gain electrons and become negatively charged anions. An anion is an atom that has gained an electron and thus has a negative charge.
Hypothesis
Attempt to explain observations.
Banded Iron Formation
Banded Iron Formations (BIF) are deep water deposits of alternating layers of iron-rich minerals and iron-poor layers. Banded iron formations are common in rocks 2.0 to 2.8 billion years old but are not formed under modern conditions.
The magma composition erupted by a hotspot beneath oceanic crust is
Basalt.
Basaltic
Basaltic magma has a relatively low silica content (45 -55%), is high in Fe, Mg, and Ca, and low in Na and K. Basaltic magmas are produced by melting of the mantle. This can occur by decompression melting at divergent plate boundaries (mid-ocean ridges, continental rifts) or at mantle hot spots.
Cinder Cone
Basaltic magmas produce cinder cones if the magma is initially gas rich. Although basaltic magma has a low viscosity that allows gases to escape easily, gases may accumulate near the top of the magma chamber prior to an eruption. In this case the early part of the eruption that taps the gas-rich magma at the top of the chamber is characterized by frothy ejection of material into the air, much like opening a shaken soda bottle. This creates a steep, conical hill called a cinder cone of pyroclastic (hot rock) fragments accumulating around and downwind from the vent. As the eruption continues and begins to tap gas poor magma from deeper in the chamber, the style of eruption changes to gentle effusion of fluid lava flows.
Shield Volcano
Basaltic magmas produce gently sloping shield volcanoes if the magma is gas poor. Shield volcanoes are gently sloping and broad volcanoes built up over time by successive thin and fluid lava flows. Eruptions of shield volcanoes are gentle and effusive eruptions of fluid basaltic lava. Shield volcanoes are found at oceanic hot spots such as Hawaii, in areas of continental rifting, and even associated with subduction zones where basaltic magma is not contaminated by melting of other materials.
Why are silicate minerals the most common group of minerals in the crust?
Because oxygen and silicon are the most common elements in the crust.
Isostasy
Because the underlying asthenosphere is weak and deforms readily, tectonic plates have the ability to rise and sink. This property is called isostasy and occurs because the crust floats on top of the mantle like icebergs in water. The thick continental crust is relatively light (density 2.2-2.5 g/cm3). The thin oceanic crust is relatively heavy (density 2.5-2.8 g/cm3). As a result the continental crust stands higher than the oceanic crust.
Orogen
Belts of deformed rocks representing mountain building episodes during collisions between continental cratons. Only the youngest orogens still stand as mountain ranges. Most orogens are eroded roots of ancient mountain ranges.
P-Waves
By measuring the time required for earthquake waves to travel through Earth by different paths, we can determine the composition of the materials through which they move. Seismic energy released by earthquakes produces two kinds of waves that provide a picture of earth's interior as they travel through it: Compressional (P) waves generate a back-and-forth motion parallel to the direction of travel. P-waves can propagate in both solids and liquids.
S-Waves
By measuring the time required for earthquake waves to travel through Earth by different paths, we can determine the composition of the materials through which they move. Seismic energy released by earthquakes produces two kinds of waves that provide a picture of earth's interior as they travel through it: Shear (S) waves move up-and-down perpendicular to the direction of wave transmission. S-waves can propagate in solids but not in liquids.
Caldera
Calderas are large circular depressions produced by the rapid, eruption of a large volume of magma. This leaves the volcano unsupported, resulting in its collapse into the drained magma chamber. Many shield and stratovolcanoes have calderas near their summits.
Ionic Bond
Cations and anions are attracted to each other due to their opposite charges and form ionic bonds. Ionic bonds are electron transfers between atoms to produce cations and anions. The mineral galena (PbS) is an example of a mineral with ionic bonding. Lead forms the Pb2+ cation and sulfur forms the S2- anion.
Vent
Central-vent eruptions build mountains of the kind most people associate with volcanoes. A vent is an opening through which lava reaches the surface.
Chemical Composition
Chemical composition refers to the specific elements (or range of elements) in a mineral and their exact proportions (or range of proportions).
Chemical Compound
Chemical compounds form when atoms of different elements combine in a specific ratio.
Cleavage
Cleavage is the tendency for a mineral to break in preferred directions along planar surfaces. Cleavage surfaces are planar directions along which cleavage occurs. They are planes along which the bonding between atoms is relatively weak as governed by crystal structure. Cleavage is described by the number of cleavage directions and their angle with each other. Cleavage can be in one direction, in two directions at 90o, in two directions not at 90o, in three directions at 90o (cubic), in three directions not at 90o (rhombohedral), in four directions (ocathedral), or in six directions (dodecahedral).
Why do composite volcanoes consist of alternating layers of pyroclastic rocks and lava flows?
Composite volcanoes are created by a mixture of explosive activity and effusive (degassed) eruptions.
The division of Earth's interior into core, mantle, and crust is used to describe differences in?
Composition We use the crust-mantle-core terminology to describe differences in chemical composition in Earth's interior. We use the lithosphere- asthenosphere terminology to describe differences the physical state and behavior. Note that the boundaries between layers with different compositions do not occur at the same depths as the boundaries between layers with different physical properties. For example, there is a change in composition when passing from crust into mantle. But there is no change in physical state or behavior at this boundary- the uppermost part of the mantle behaves in the same way that the crust does because it is still far enough below its melting temperature to be a rigid, brittle solid. The transition to a softer, more pliable solid occurs further down within the mantle and this change in behavior occurs with no change in composition.
Describe the classification and naming of igneous rocks.
Composition and texture Intrusive, extrusive, pyroclastic Felsic, intermediate, mafic, ultra mafic
Composition
Composition refers the types and relative abundances of minerals present, which depends on the composition of the magma from which the rock was crystallized.
Silicate
Contain the silicate ion, make up 95% of the Earth's crust. Minerals containing the silicate ion are called silicates. The silicate ions can occur as isolated tetrahedrons or be linked in a variety of ways to form different crystal structures, such as single or double chains, sheets, or frameworks.
Contamination-Magma Mixing
Contamination occurs as rising magma assimilates surrounding rock. Heat from the rising magma also melts the surrounding rock, creating a second magma. The two magmas may mix (magma mixing) to produce a new composition.
Continental Crust
Continental crust is less dense and thicker, with a chemical composition similar to the rock type granite (made of the elements Si, O, Al, K, Na).
Oceanic crust is produced by seafloor spreading. How is continental crust produced?
Continental crust is produced at subduction zones as buoyant materials on the subducting plate are accreted to the leading edge of the overriding plate, while the remainder of the plate (due to its higher density) is subducted into the mantle. Introduction of water into the mantle by the subducting plate causes melting in the upper mantle producing magmas that are richer in silica and more like the continental crust than they are the mantle or the subducting plate. These magmas may erupt at the surface but most crystallize within the crust of the overriding plate as intrusion. Either way, more material is added to the continental plate. Both terrane accretion and partial melting makes continental crust by separating out buoyant materials from the subducting plate.
What causes plates to move?
Continental drift, seafloor spreading, subduction
Continental Shield
Continental shields are assemblages of ancient cratons and their associated orogens sutured together by tectonic collisions.
Convection
Convection is the process where hot material, heated from below, rises and is replaced by the sinking of cold material. Convection currents in the asthenosphere drag the rigid lithosphere along for the ride. This is the driving force of plate tectonics.
Igneous Rock
Created through the cooling and solidification of magma.
Crystal Habit
Crystal habit is the characteristic crystal form or shape of each mineral. Mineral crystals that grew without physical interference or "crowding" from adjacent mineral crystals will best display the characteristic crystal habit of that mineral. Some crystal habits you will observe in your lab specimens include cubic, tabular, sheet, prismatic, and hexagonal. A mineral with cubic habit has three dimensions of approximately equal length, like a cube. Tabular minerals have two axes that are long while the third dimension is shorter, like a book. A mineral with sheet-like habit has two long axes and one very short axis, like a sheet of paper. Prismatic habits are the opposite: one long axis and two shot axes, like a rod or needle. Minerals with hexagonal habit have six dimensions, like a hexagon, usually of equal length. Likewise, octahedral crystals have eight axes. Equally important in identification is the absence of any distinctive habit. Such minerals are said to be massive, meaning they lack distinctive geometric crystal forms.
Crystal Structure
Crystalline structure is the orderly, regularly repeating internal atomic arrangement in which the atoms are packed together in a mineral. Most minerals are compounds, containing more than one element. A few minerals are composed of a single element (examples are diamond, graphite, gold, copper, and sulfur).
Tectonic Setting
Describes the geologic environment of an area relative to any nearby plate boundaries or hot spots. Tectonic settings include divergent, convergent, and transform plate boundaries as well as hot spots. Each tectonic setting produces a characteristic style of volcanism.
Fractional Crystallization
Different magma compositions can also be produced from the same parent magma by fractional crystallization: the cooling and separation of minerals from the remaining magma. As magma cools, minerals crystallize in a specific sequence called Bowen's reaction series.
How do we know the composition and structure of Earth's interior?
Direct observations are provided by drilling to as deep as 15 km (10 miles). There are also exposures of mantle rocks at the surface in a few places (brought up from » 50 km (30 miles) depth). Material erupted by volcanoes (brought up from » 200 km (120 miles) depth) also gives us a glimpse of what's inside the Earth. The overall mass and density of the earth is known from the strength of its gravitational field. The thickness and density of the mantle is known from studies of seismic waves traveling through the earth's interior. The composition of the mantle is also known from studying mantle rocks in the few places where they were left exposed at the surface due to tectonic forces. This allows us to calculate the density of the mantle, as well as the crust.
Provide a modern-day example of each type of plate boundary.
Divergent: Gulf of California spreading center and extension in the Basin and Range and Rio Grande Rift (a failing continental rift) Transform: the San Andreas and related fault systems Convergent: the Cascadia Subduction Zone Hot Spot: the Yellowstone hot spot
***What is the basic geologic setting of the Pacific Northwest?
Dominated by the Cascadia Subduction Zone. The subduction zone is a fault that extends from mid-Vancouver Island to Northern California. Oceanic plates are subducted beneath the North American (continental) plate. Hazards associated with this process include earthquakes and tsunamis as well as the volcanoes of the Cascade Range. Juan De Fuca plate moving under north american plate. In addition to occasionally producing great earthquakes, the process of subduction is also responsible for the chain of volcanoes that define the Cascade Range of Washington, Oregon, and northern California, including MountRainer, Mount St. Helens, Mount Hood, the Three Sisters, Crater Lake, and Mount Shasta.
How did the discovery of magnetic reversals confirm the sea floor spreading hypothesis?
During the 1950's in WWII there were many discoveries made about the Earths magnetism and with the mapping of the ocean floor from technologies created then we found a mechanism for continental drift called seafloor spreading. Magnetic field direction recorded in the rocks of the seafloor were mapped which showed a pattern of rocks recording alternating periods of normal and reversed polarity which are seen on either side of the mid ocean ridge. So when looking at the finding of the age distribution and magnetic symmetry of the sea floor the idea of seafloor spreading came about. Seafloor spreading comes from magma rising at mid ocean ridges which then cools and forms new ocean crust. While this new crust is formed old crust is pushed away towards the outside which explains the age distribution and magnetic polarity found.
How is Earth unique in our Solar System?
Earth may be the only planetary body in the solar system with active plate tectonic. Plate tectonics, by recycling earth materials, helps maintain the life-support system of this planet: An atmosphere with just enough greenhouse gases (such as carbon dioxide) to keep the earth the right temperature for liquid water to be present. Liquid water is a requirement for all life as we know it. Without active plate tectonics, the Earth would resemble its nearest neighbors. Earth is also the only planetary body in our solar system where large quantities of water exist in all three phases: liquid water, water vapor, and ice, making Earth the "Blue Planet". Earth is unique in the solar system because it has an oxygen rich atmosphere provided by photosynthetic organisms. Without photosynthesis, Earth would have an atmosphere much like its neighbors. Earth is also unique because surface pressure and temperature conditions allow water to exist in a liquid state on Earth.
Describe the transformations of Earth's environment from oxygen-starved to oxygen-rich, and the evidence for this in the rock record.
Earth supports life because life evolved on earth. The first primitive life forms evolved while modifying their environment, especially the composition of atmosphere, allowing the Earth to support more advanced forms of life. Earth's early atmosphere (4.4 to 4.0 billion years ago) was composed of water vapor (H2O), carbon dioxide (CO2), nitrogen (N2), hydrogen cyanide (HCN), ammonia (NH3), methane (CH4), sulfur, iodine, bromine, chlorine, and argon. High temperatures resulted in water existing only as water vapor. Once the atmosphere began cooling, water vapor condensed as precipitation and formed the oceans. Chemosynthetic bacteria first appeared at 3.6 billion years ago. At this time life starts to modify the atmosphere through photosynthesis, which consumes carbon dioxide and releases oxygen. As life develops, evolves, and grows the amount of oxygen present in the atmosphere grows from <1% to 21%. Today's atmosphere consists of Nitrogen (N2) 78%, Oxygen (O2) 21%, Argon (Ar) 1%, carbon dioxide (CO2) 0.036%. Observation of rusting (oxidation) of iron in different types of rocks allows geologists to make inferences about the levels of oxygen in the atmosphere. Banded Iron Formations (BIF) are deep water deposits of alternating layers of iron-rich minerals and iron-poor layers. Banded iron formations are common in rocks 2.0 to 2.8 billion years old but are not formed under modern conditions. They represent the transformation of Earth from an oxygen starved (reducing) environment to an oxygen rich (oxidizing) environment. In the absence of free oxygen, iron is found in its reduced form which is soluble and remains dissolved in seawater. As the Earth became oxygenated, the iron was converted from its reduced to its oxidized form by reaction with free oxygen to make ion oxides (rust) which are insoluble and are precipitated from seawater as banded iron formations.
Earth's interior is hot because?
Earth's interior is hot because the process that formed Earth (accretion) generated large amounts of heat. Additional heat has been added through geologic time by radioactive decay of unstable isotopes (heat is a byproduct of the decay process). Molten rock or magma is actually rare in earth's interior - only the outer core is hot enough to be above the melting point for material of that composition under that amount of pressure. Earth's interior is mostly magma.
Wilson Cycle
Eventually, a passive continental margin develops into a new subduction zone as the adjacent oceanic crust becomes older, colder, and denser. The ocean basin, while still spreading at the mid-ocean ridge, starts to grow smaller as oceanic crust is subducted. As the intervening ocean basin disappears the continents are drawn into a new round of collision, albeit in a new place. This cycle of continent formation, breakup, and re-assembly is called the Wilson Cycle.
Closed System
Exchanges energy with its surroundings, but not matter. ex: sealed ballon Earth freely gains energy from the sun and looses energy to space, gains and loses of matter are negligible, all waste and pollutants generated on earth stay here, finite supply of resources.
Extrusive
Extrusive igneous rocks: Crystallized quickly from cooling of lava erupted at the surface, crystals are generally small.
The mineral ________ is a Na or K- bearing silicate mineral common in the continental crust.
Feldspar.
Felsic
Felsic (rhyolitic) igneous rocks are produced by melting of continental crust. Felsic igneous rocks consist of mostly light colored minerals rich in silica, K, and Na, and are poor in Fe, Mg, and Ca.
Apahnitic
Fine-grained, extrusive igneous rock texture with small crystals that may be difficult to see without magnification is called aphanitic.
Felsic
First minerals to melt are those with low melting points and are high in silica. The initial melt is therefor also high in silica making it felsic.
Fissure
Fissure eruptions build broad lava plateaus Eruptions may also take along elongated cracks called fissures or rifts where weaknesses in the crust provide a path for molten rock to reach the surface. Fissures can form locally on the flanks of a volcano or affect large regions where divergent stresses are rifting the crust.
Magnetic Reversal
For reasons that are not understood, Earth's magnetic field occasionally reverses polarity. In other words, the magnetic field flips direction (a magnetic reversal). The geologic record provides evidence of 171 field reversals in the last 71 million years. Time is divided into periods of predominately normal polarity or predominately reverse polarity. Periods are called magnetic chrons. Within each chron there can be subchrons (times of opposite polarity). Today we are in a period of normal polarity (the Brunhes chron).
How do igneous rocks form?
Form by the cooling and crystallization of magma either below ground or by the eruption of lava at the surface.
Metamorphic Rock
Formed by the effects of pressure and heat on existing rocks.
Which of the following minerals is a sulfide mineral?
Galena.
Hardness
Hardness is a mineral's resistance to scratching. The degree of hardness is determined by observing the comparative ease or difficulty with which one mineral is scratched by another.
Open System
Have boundaries that permit the exchange of both matter and energy with their surroundings. ex: human body
Effusive
Higher temperature, lower viscosity magmas tend to have lower gas contents and produce gentler, effusive eruptions.
What controls the grain size and texture in igneous rocks?
How the rock cooled.
Covalent Bond
If two atoms both need an electron or electrons to fill their outermost shells, they can share an electron and form a covalent bond. In covalent bonding atoms share electrons rather than transferring them, creating a strong bond. A molecule of water (H2O) is an example of a covalently bonded compound.
Describe the identification and naming of igneous rocks.
Igneous rocks are formed by the cooling and crystallization of magma above or below ground by the eruption of lava at the surface. You can classify igneous rocks by composition and texture. Composition refers to the types and amounts of certain minerals in the rock which can depend on the magma the rock crystalized from. Texture can be the shape, size, and arrangement of present minerals and will depend on how the crystallization of the rock occurred. Igneous rocks can be intrusive or extrusive depending on where they were crystalized. They can also be felsic, intermediate, magic, or ultramafic depending on its composition of minerals. When you look at the composition and texture that is when you can put a name to the rock. Course grained intrusive rocks with large crystals are called phaneritic. Fine grained extrusive rocks with small crystals are called aphanitic. Porphyritic texture is mostly fine-grained with some larger crystals. Vesicular texture means the rock has void bubbles created from gas. Pyroclastic rocks are from when molten material erupts and cools as it falls and creates the commonly known pumice texture. Felsic rocks are composed of mostly light minerals and contain mostly quartz and potassium feldspar and are usually granite if intrusive and rhyolite if extrusive. Intermediate rocks have a balance of light and dark minerals. Dacite is a quartz rich extrusive intermediate rock and the intrusive version is granodiorite. Mafic rocks are composed of mostly dark minerals like iron and magnesium. Gabbaro is an example of this composed of mostly magic minerals like pyroxene, amphiboles and olivine. Ultramafic rocks are coarse grained and have olivine being the most abundant but sometimes the only mineral present is peridotite.
Vesicular
Igneous rocks with a vesicular texture have void spaces (bubbles) left by escaping gas.
Volcanic Arc
In a collision between two plates of oceanic crust, the older and denser crust gets subducted beneath the younger and lighter crust. A deep-sea trench marks the subduction zone at the surface. As subducted slab descends into the mantle, it partially melts. The rising magma produces a chain of volcanoes on the overriding, younger oceanic plate called a volcanic island arc.
Metallic Bond
In metallic bonding: closely packed atoms share electrons in higher energy-level shells among several atoms. Because the electrons are loosely held, they can drift from one atom to another. This is why metallic compounds are excellent conductors of electricity.
Framework
In network or framework silicates, every oxygen atom in a silicate tetrahedra is shared with another silicate tetrahedra, linking the tetrahedra in a complex three-dimensional network. Examples of framework silicates are the feldspar group and quartz.
Inclination
Inclination is the angle (dip) of the magnetic field lines with respect to the surface of the Earth and varies from 0o (horizontal) at the magnetic equator to 90o (vertical) at the magnetic poles.
Infiltration
Infiltration is the movement of liquid water downward from the land surface into and through the soil and rock.
Inner Core
Inner core is solid iron (>5140 km depth).
Intermediate
Intermediate (andesitic) igneous rocks are produced by melting of water rich subducted oceanic crust. Intermediate igneous rocks contain a more equal mixture of light and dark minerals and include dacite, granodiorite, andesite, and diorite.
Intrusive
Intrusive igneous rocks: Crystallized slowly from cooling of magma beneath the Earth surface, allowing large crystals time to form.
Explain the four types of bonding.
Ionic, covalent, metallic, van der walls
System
Is any portion of the universe that can be isolated from the rest of the universe for observing and measuring change.
Atomic Number
Is the number of protons in an atom.
Abyssal Plain
Is underlain by older oceanic crust that has moved away from the ridge, cooled, and subsided.
Eruption of rhyolite magma that has already degassed tends to produce
Lava Domes: rhyolite magma is high in viscosity (meaning it is thick and pasty) by virtue of its high silica content and low temperature (compared to basalt). The high viscosity of rhyolite prevents it from flowing away from the vent where it is erupted. Instead, rhyolite piles up are the vent forming a steep, dome shaped structure - a lava dome. Meanwhile, shield volcanoes and cinder cones are associated with eruptions of low viscosity basalt, either effusively when little gas is present (shield) or a foamy or frothy manner when large amounts of gas are present (cinder cones). Intermediate viscosity andesite produces composite volcanoes that erupt both explosively (when the magma is gas charged) and effusively (after the magma has de-gassed).
Lava Flow
Lava flows are effusive eruptions of magma from a volcanic vent or fissure. Lava flows are often basaltic in composition because more viscous andesitic and rhyolitic magma tends to erupt explosively through the air due to higher gas contents. Lower viscosity basaltic lava flows also travel further from the source than more viscous andesitic and rhyolitic lava flows.
Pahoehoe
Low viscosity, high temp
Explosive
Lower temperature, higher viscosity magmas tend to have higher gas contents and produce violent, explosive eruptions. The gas content of magma is extremely important in a driving an explosive eruption. While under pressure, gases are kept dissolved in the magma. As pressure is reduced, for example as magma rises towards the surface, gases come out of solution to form bubbles. As the magma continues to rise towards lower pressures, the bubbles expand and grow, driving the magma towards the surface. The largest and the most violent eruptions are associated with silica-rich magmas having high dissolved-gas content.
Decompression Melting
Lowering the pressure. Because the melting point is a function of both temperature and pressure, lowering the pressure also lowers the temperature at which melting occurs. This is called decompression melting and occurs when mantle material migrates upwards to areas of lower pressure. This is common at divergent plate boundaries as well as hot spots.
Luster
Luster is the quality and intensity of light reflected from a mineral. Metallic (like a polished metal surface). Vitreous (glassy). Resinous (resin): the look of dried glue or amber. Pearly (pearl): the iridescent look of a pearl. Greasy (as if the surface were covered by a film of oil). Earthy (the look of dry soil) Dull (a non-reflective surface of any kind)
Mafic
Mafic (basaltic) igneous rocks are produced by melting of the Earth's mantle. Mafic igneous rocks consist of mostly darker minerals rich in Fe, Mg, and Ca, and poor in K, Na, and silica.
Gabbro-Basalt
Mafic igneous rocks are composed mostly of dark colored minerals rich in iron and magnesium. Dark-colored diorite grades into gabbro. Gabbro is composed mostly of mafic minerals such as pyroxene, amphiboles, and olivine. Plagioclase feldspar is also present, but in smaller amounts than in diorite. Basalt is the extrusive equivalent of gabbro. Basalt is the most common kind of extrusive igneous rock and makes up most of the oceanic crust.
Why is a volcano's style of eruption related to its magma's silica content?
Magma has a wide range of compositions, but silica (SiO2) always dominates the mix. Magma has high temperatures. Magma is fluid—it has the ability to flow. Most magma actually is a mixture of liquid (often referred to as melt) and solid mineral grains. Basaltic magmas (50% SiO2) are erupted by approximately 80 percent of volcanoes worldwide (the seafloor worldwide is mostly basalt). Andesitic magmas (60% SiO2) are about 10 percent of the total magma. Magma from subduction zone volcanoes such as Mount St. Helens in Washington State and Krakatau in Indonesia is usually andesitic. Rhyolitic magmas (70% SiO2) are about 10 percent of the total magma. Magmas erupted from volcanoes that once were active at Yellowstone Park are mostly rhyolitic.
Magma
Magma is a liquid with a silicate composition (50-90% Si-Al-O). Magma may also contain gases, either dissolved or exsolved (bubbles); and solids such as minerals crystallizing from the liquid or unmelted residual rock. Volcanoes and volcanic activity occur in tectonic settings where melting of rocks produces magma, a mixture of molten rock and dissolved gases. Made by: raising temp, lowering pressure, adding impurities
Explain the relationships between magma composition, crustal thickness, fractional crystallization, and tectonic setting.
Magma is generally defined as a liquid with a silicate composition which may contain gases and solids. Volcanoes and other volcanic activity can occur in tectonic settings where melting of rocks create magma and that magma when it erupts to the surface is called lava. There are 3 different types of magma including basaltic, andesitic, and rhyolitic. You can get those different types of magma a few different ways including fractional crystallization which is the cooling and separation of minerals from the remaining magma. When magma cools minerals crystalize in a certain sequence that we refer to as Bowens reaction series. The minerals low in silica crystalize first. Knowing this we then know that the remaining magma is higher in silica. So as the magma continues to crystalize we know that the residual magma is getting higher and higher in silica. The magma goes from its original basaltic to andesitic and then rhyolitic in regards to its composition as the low silica minerals are crystalized and removed. Volcanoes happen when magma reaches the surface of the earth this can disrupt plate tectonics. The words distribution of volcanoes is explained by plate tectonics because melting happens in certain tectonics settings. Volcanoes are found along subduction zones, mis-ocean ridges, continental rifts or over hot spots. The different compositions of magma can effect the crustal thickness in certain places on tectonics plates. Basalt (from melting of mantle) found in every tectonic setting where mantle melts due to decompression (hotspot, continental rift, ocean ridge) or addition of water (subduction zones). Higher silica andesite and rhyolite only found on thicker crust where fractional crystallization of mantle basalt and contamination with crustal material produces magmas with higher silica content (subduction zones with volcanic arc on continental crust), continental hotspot
Pluton
Magma need not reach the surface by volcanic eruption, instead it may be intruded and cool far underground to form plutons of igneous rock in a variety of shapes and sizes.
Lava
Magma that erupts on the surface is called lava.
Which of the following statements about magma viscosity is NOT true?
Magma that is high viscosity will be thin, fluid, and fast flowing
Partial Melting
Magmas of different compositions can be generated from the same parent material by different amounts of partial melting. As rock is heated, the first magma to form is richer in silica than the parent rock because silica rich minerals melt at lower temperatures. As melting continues, minerals poorer in silica are melted and the magma composition becomes more similar to the parent material. Complete melting results in a magma with the same composition as the parent material.
Mantle
Makes up most of the earth in terms of volume. The mantle has an intermediate composition, mostly magnesium (Mg), iron (Fe), and silicon (Si). The mantle is 2,900 km (2000 miles) thick.
Lava with low viscosity is found at which volcano?
Mauna Loa, Hawaii
How do you get magmas with different compositions?
Melt different starting materials, partial melting, fractional crystallization.
Fracture
Minerals also break or fracture along irregular surfaces.
Polymorphism
Minerals that are polymorphs have the same chemical composition but a different crystalline structure (and hence different physical properties). Examples include: C Graphite, Diamond CaCO3 Calcite, Aragonite FeS2 Pyrite, Marcasite SiO2 Quartz, Cristobalite
Explain why geologists believe that the Earth's core is made mostly of iron.
Need the core to not only be dense (as shown by strength of gravitational field) but also be metallic (as shown by presence of strong magnetic field). Meteorites tell us why iron and not some other dense metal because they show us that iron is the most common dense, metallic element
Divergent plate boundary
Occur where plates are being pulled apart. Where a continent is being pulled apart a new divergent boundary called a continental rift valley is created. The East African Rift Valley is an example of a continental rift. Continental rift valleys represent the earliest stage in the development of a new ocean basin as a single continental plate splits into two fragments as new oceanic crust grows between them. New oceanic crust is created at divergent plate boundaries as two plates pull away from each other. Divergent plate boundaries are associated with extensional stress, shallow earthquakes, and basaltic volcanism. Examples include the mid-ocean ridges such as the Mid-Atlantic Ridge.
Convergent Plate Boundary
Occur where plates are moving together or colliding. Ocean-Ocean: collision between two plates composed of oceanic crust; older denser oceanic crust is subducted and destroyed. Ocean-Continent: collision between oceanic and continental crust; oceanic crust is subducted by the continent and destroyed. Continent-Continent: collision between two plates composed of continental crust; both are too light to be subducted.
Transform Plate Boundary
Occur where two plates are sliding past each other in different directions. The boundary is marked by a system of faults. Motion between the plates is not always smooth due to friction; instead the plates periodically lurch past each other, resulting in earthquakes. Shear stresses crumple the edges of the plates and rocks on either side of the faults. California's San Andreas Fault is an excellent example of a transform plate boundary between the Pacific and North American plates.
Statements about Continental and Oceanic Crusts:
Oceanic crust is lower in Fe and Mg Continental crust is older Continental crust is thicker Oceanic crust is denser
Chain
Olivine and garnet are examples of silicate minerals in which the crystal structures consist of isolated silicate tetrahedra that are not linked in any way. The pyroxene group consists of single chain silicates and are common minerals in igneous and metamorphic rocks (example: the mineral augite). The amphibole group are double chain silicates and are also common in igneous and metamorphic rocks (example: the mineral hornblende). The pyroxenes and the amphiboles are hard to tell apart (similar color, hardness, etc.). The best way to distinguish them is by their cleavage. The cleavages in pyroxene are right angles (90o). The cleavages in amphibole are at 120o.
Theory
Once a hypothesis has been accepted by most researchers in a field, it is considered a scientific theory. Hypotheses gradually gain acceptance over many years through repeated testing and modification to become theories. A theory is a hypothesis that has withstood repeated scrutiny over time.
What is the difference between a hypothesis and a scientific theory?
Once a hypothesis has been accepted by most researchers in a field, it is considered a scientific theory. Hypotheses gradually gain acceptance over many years through repeated testing and modification to become theories. A theory is a hypothesis that has withstood repeated scrutiny over time.
Differentiation
Once in a molten state, the Earth segregated into layers of different composition on the basis of density. This process is called differentiation. Lighter elements (silicon, aluminum, sodium, and potassium) rose to form the crust. Heavier elements (like iron) sank to form the core, with a residual mantle of intermediate density in between the crust and the core. This left the earth segregated into layers of different densities and compositions.
Outer Core
Outer core is made of liquid iron (2890-5140 km depth). Layer of the earth that is thought to be a liquid.
Pahoehoe
Pahoehoe: higher temperature, lower viscosity, smooth ropy surface texture
A poryphyritic texture indicates an igneous rock that
Partially cooled underground and was then erupted on the surface.
Accretion
Planetary accretion is the collision of larger and larger planetary objects. One of the largest accretionary events was a collision between the proto-Earth and another planetary object roughly the size of Mars. This event left the Earth's rotational axis tilted and ejected material into orbit around the Earth. This material in turn accreted to form the Moon. Objects travel at very high speeds through space. This kinetic energy of motion is converted on impact to heat during accretion. As Earth grew larger and larger from continual impacts, its temperature increased. The radioactive decay of materials like uranium, thorium and potassium also added heat to Earth's interior. The heat of planetary accretion resulted in large scale melting of the inner planets (including Earth) The process by which the planets, including Earth, were formed by gravitational attraction of matter.
Why is plate tectonics important?
Plate tectonics explains the global distribution of earthquakes, volcanoes, and mountain ranges. Plate tectonics is also responsible for creating and destroying ocean basins as well as building and rearranging the continents. Through the processes of subduction and volcanism, plate tectonics recycles earth materials. Our atmosphere is also maintained through volcanic degassing and climate regulated by controlling the atmospheric carbon dioxide content and the magnitude of the greenhouse effect.
Porphyritic
Porphyritic texture is mostly fine grained matrix with embedded larger crystals, indicating partial crystallization underground followed by eruption onto surface. Porphyry is an igneous rock in which 50% or more of the rock is coarse mineral grains scattered through a mixture of fine mineral grains. The isolated large grains are phenocrysts.
How are geologic processes, geologic hazards, and geologic resources related?
Potentially hazardous geologic processes include: Erosion: responsible for landslides, subsidence, flooding Weathering: responsible for landslides and subsidence Plate tectonics: responsible for earthquakes, volcanism, landslides, subsidence. Geologic processes also supply many resources that our high-tech society needs. These resources include energy resources, minerals and ores, building materials, soils and fertilizers for agriculture, and last but not least the clean air and water needed to support life. We depend on geologic energy resources to power our high-tech society. Fossil fuels such as oil, coal, and natural gas currently supply most of the UnitedState's energy needs. The development of these resources has entailed some of the largest construction projects ever under taken. The utilization of geologic resources presents a variety of concomitant environmental problems associated with resource extraction, refinement, use, and disposal. Oil must be recovered from subsurface reservoirs by drilling wells, which disrupt the natural landscape
Precipitation
Precipitation is the change of atmospheric water vapor to liquid (rain) or solid (snow).
Pumice
Pumice consist of very light pyroclastic materials erupted through the air. Pumice is typically both light in color, due to a felsic composition; and light in density, because of the large amount of void space due to escaping volcanic gases.
Igneous rocks produced by explosive volcanic activity will have what kind of texture?
Pyroclastic
Pyroclastic Flow
Pyroclastic flows are high-density mixtures of hot, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds. Most pyroclastic flows consist of two parts: a basal flow of coarse fragments that moves along the ground, and a turbulent cloud of ash that rises above the basal flow. Ash may fall from this cloud over a wide area downwind from the pyroclastic flow. When the mixture of hot gases and pyroclasts is more dense than the atmosphere, the turbulent mixture flows down the side of the volcano. Pyroclastic flows are a hot, highly mobile flow of tephra that rushes down the flank of a volcano during a major eruption and are also known as nuée ardente (glowing avalanches).
Pyroclastic
Pyroclastic rocks from when molten material is erupted explosively through the air and cools as it falls. Examples of pyroclastic rocks include scoria, cinders, pumice, and tuff.
Explain the different physical properties that are useful for identifying minerals.
Readily observable physical properties such as color, luster, streak, hardness, cleavage, and crystal habit, because they reflect the chemical composition and crystal structure of a mineral, are very useful in identifying minerals.
Red Beds
Red Beds are another type of iron-rich rock formation and are colored red because of the mineral hematite. Hematite forms in the process of oxidation of other iron minerals.
Flood Basalt
Regional fissure systems can also feed voluminous outpourings of basalts called flood basalts, which cover large areas of the ocean floor. Flood basalts can also be found on the continents.
Rhyolitic
Rhyolitic magma has a high silica content (65-75%), is high in Na and K, and low in Fe, Mg, and Ca. Rhyolitic magmas are produced by melting continental crust. This occurs when hot material migrates upward from the mantle and melts the surrounding crust, such as when a continent passes over a hot spot.
Dome Volcano-Lava Dome
Rhyolitic magmas produce steep-sided dome volcanoes. Lava domes consist of high viscosity rhyolitic magma. Because rhyolitic magma is very sticky and pasty, eruptions of rhyolitic volcanic domes are mostly explosive and build a steep sided dome that is prone to collapse. Extrusion of a small rhyolitic lava dome often ends an eruption sequence at a stratovolcano, allowing pressure to build up by plugging the volcano's vent until it is cleared by the next explosive eruption.
Mid-ocean Ridge
Ridge Push: as new crust is created at the ridge, it pushes the older crust aside. Is the site of seafloor spreading and the active plate boundary.
Xenolith
Rising magma can dislodge fragments of the overlying rock, and the dislodged blocks, being cooler and more dense than the magma, sink. This process can produce xenoliths. Any rock fragment still enclosed in a magmatic body when it solidifies is a xenolith.
Normal Polarity
Rocks indicating a field direction the same as today's (magnetic north pole near the geographic North Pole) are said to have normal polarity.
Reversed Polarity
Rocks indicating the opposite field (magnetic north pole near the geographic South Pole) have reversed polarity.
Obsidian
Rocks such as obsidian or volcanic glass are glassy with no crystal structure, and are formed by very rapid cooling on the surface. Extrusive igneous rocks that are largely or wholly glassy are called obsidian. Although most obsidian is rhyolitic in composition, it may appear mafic because the small amount of Fe and Mg present is dispersed throughout the rock, making it appear dark. This is analogous to a small amount of chocolate syrup added to a glass of milk which when stirred makes the milk appear chocolate.
Vitreous
Rocks such as obsidian or volcanic glass are glassy with no crystal structure, and are formed by very rapid cooling on the surface. There is no crystal structure because atoms lack time to organize themselves into minerals. Such rocks are said to have vitreous texture.
How did seafloor spreading revive Alfred Wegener's ideas about continental drift?
Sea floor spreading provided a viable mechanism for moving the continents.
Seafloor Spreading
Seafloor spreading is a result of rising magma at the mid-ocean ridges which cools to form new ocean crust. As new crust is formed the older crust is pushed away from the ridge. This explains both the age distribution of the seafloor and the symmetry with respect to the ridge. The drifting continents do not plow through the seafloor, instead the seafloor acts as a giant conveyor belt in which the embedded continents are taken along for the ride. Discoveries about Earth's magnetism in the 1950s and mapping of the ocean floor made possible by technologies developed during World War II eventually provided a mechanism for continental drift called seafloor spreading. The topography of the seafloor was found to be dominated by huge underwater mountain ranges called mid-ocean ridges running through the ocean basins like seams on a baseball. Another curious feature of the ocean basins is the narrow but very deep trenches, most notably along the western margin of the Pacific Ocean. The age of rocks on the seafloor shows an orderly distribution. Rocks were youngest along the mid-ocean ridges and progressively older away from the mid-ocean ridges. The thickness of seafloor sediments also supports this age distribution. Sediments are thinner toward the ridge because they have had less time to accumulate. Although the oldest rocks on the continents (4 billion years old) are nearly as old as the earth itself, nowhere on the seafloor are rocks found to be older than about 200 million years. Bands of rocks recording alternating periods of normal and reversed polarity are symmetric on either side of the mid-ocean ridge.
Sheet
Sheet silicates include the group of minerals called micas. Because of their crystal structure, a sheet network, micas display perfect cleavage in once direction, breaking into sheets. These sheets can be as little as one molecule in width!
What types of volcanoes are associated with eruptions of basaltic magma? Name one example of each of these types of volcanoes, and explain how their shapes are related to their eruptive style.
Shield volcanoes are a result of an eruption of basaltic magma like Mauna Loa in Hawaii. Another example of an eruption from basaltic magma is cinder comes like the Sunset crater in Arizona. Basaltic magma is generally around 50% silica so its slightly less viscous that rhyolitic magma. This means that basaltic magma has a tendency to be very fluid and flow a long way. The eruption of this very viscous thin magma allows the magma to flow a long way creating broad and slightly sloped shield volcanos. When the basaltic magma has more gas in it though it erupts differently creating cinder cones. this comes from a frothy eruption that send material flying through the air. This creates a steep conical hill, where the rock fragments accumulate around and downwind from the vent.
Silicate Ion
Silicon and oxygen are by far the most common elements in the Earth's crust, making up more than 70% of the continental crust by weight. They combine to form an ion called the silicate ion (SiO4) with a four-sided shape called a tetrahedron.
Sill
Sills are also tabular and sheet-like, like a dike, but run parallel to the layering or fabric of the rocks into which it intrudes.
Trench
Slab Pull: The weight of the subducted slab drags the rest of the plate into the trench, until it melts. One plate going under the other
Streak
Streak is the thin layer of powdered material left when a specimen is rubbed on an unglazed ceramic plate. Streak is more reliable than color for identification.
Which property can be used to distinguish hematite from magnetite?
Streak.
Buoyant materials are added to the edge of continents by?
Subduction of the surrounding oceanic crust.
Composite volcanoes are found only in which tectonic setting?
Subduction zone
Earth System
Subsets of the earth system are open systems, dynamic and interconnected, with matter and energy continuously exchanged. There are four Earth systems: atmosphere, hydrosphere, biosphere, and the geosphere.
Identifying Feldspar
Tabular or blocky crystal habit Two good cleavage directions at nearly 90o Non-metallic or vitreous luster Fairly hard (~6-7) Generally light in color: white, pink, etc., with a white streak
Texture
Texture refers to the size, shape, and arrangement of minerals present. The texture of igneous rocks depends on how crystallization occurred. Igneous rock textures are determined by how the rock formed, in particular the cooling rate. Rocks that cool slowly underground have large mineral crystals, phaneritic texture, and are said to be intrusive. Rocks that cool quickly by eruption at the surface have small mineral crystals, aphanitic texture, and are said to be extrusive. Extrusive rocks can also take on more distinctive textures if they have a lot of gas (vesicular), are erupted explosively through the air (pyroclastic), or cool so quickly that individual mineral crystals do not form (vitreous). Finally, magma may partially to cool slowly underground and then get erupted at the surface where the remaining magma cools very quickly. Such rocks have porphyritic texture and consist of large mineral crystals embedded in a fine grained matrix.
What is a system? Describe the components that make up the Earth System. Is the earth an open or closed system? Why?
The Earth receives energy from the sun and releases heat energy into space. Meteorites also fall to Earth, and light gases such as hydrogen can escape to space from the top of the atmosphere. Earth is best thought of as a closed system. This is because the amount of matter that the Earth gains from or loses to the surrounding space is, for all practical purposes, negligible compared to the size of the Earth. Because the amount of matter in a closed system is fixed, all the earth resources we have today are all we will ever have. Not only are resources limited, but all waste remains within the system. In other words, because the Earth is essentially a closed system, there is no "away" to throw things to. Changes within a closed system will eventually affect other parts of the system. Rigid and brittle lithosphere made of crust and uppermost mantle where rock is cold and hard; softer and pliable asthenosphere is the remainder of the upper mantle where rock is warm and soft. Crust composed of light silicates (Na or K bearing), mantle of heavier silicates (Mg or Fe bearing), core of dense metals (mostly iron but also nickel and others).
Continental Slope
The abyssal plains end abruptly at the continental slope where the crust transitions to lighter and more buoyant continental crust.
Asthenosphere
The asthenosphere is the plastic region of upper mantle were rocks are weak and easily deformed because they are close to their melting point (up to 670 km depth).
Atmosphere
The atmosphere consists of the gases surrounding the Earth. The atmosphere extends approximately 500 km above Earth's surface and the lowest level composes the climate system that maintains suitable conditions for life on Earth. The atmosphere is primarily composed of nitrogen (N2, 78%), oxygen (O2, 21%), and argon (Ar, 1%). Other important components include water (H2O, 0-7%), ozone (O, 0-0.01%), and carbondioxide (CO2, 0.01-0.1%).
Atomic Mass Number
The atomic mass number is the total number of protons and neutrons in an atom.
Biosphere
The biosphere includes all of Earth's living organisms as well as dead organic matter not yet decayed. The biosphere may also be thought of as the inhabited portion of the earth and includes the hydrosphere, the lower portion of the atmosphere, and the upper portion of the geosphere.
Core
The core is the innermost densest layer composed of heavier elements, namely iron (Fe) and nickel (Ni). The center of Earth is 6,300 km (4,000 miles) below the surface.
Crust
The crust is the thin outer shell composed of light elements like oxygen (O), silicon (Si), and aluminum (Al). The crust is from 10 to 70 km thick (5 to 30 miles). The major topographic features of the crust including Mt.Everest (~9 km high) and the Mariana Trench (11 km deep) are a result of plate tectonic activity.
Polarity
The flow generates an electrical current, in turn creating a magnetic field. Earth's magnetic field resembles that of a simple bar magnetic with two poles of opposite polarity. Because the magnetic field is generated by Earth's rotation, the magnetic poles are within a few degrees of the rotational (geographic) poles.
Geosphere
The geosphere (or lithosphere) consists of the geologic materials including rocks, soils, and the Earth's interior. The geosphere is the solid Earth including the continental and oceanic crust as well as layers of the Earth's interior. Geosphere is divided into the crust, mantle, and core. The deeper layers are composed of heavier materials and are hotter, denser and under greater pressure than the outer layers. Ninety-four percent of the Earth is composed of oxygen, iron, silica, and magnesium.
Hydrologic Cycle
The hydrologic cycle describes the movements (fluxes) of water between various reservoirs or places where water is found. Precipitation, evaporation, transpiration, infiltration.
Lithosphere
The lithosphere is the cold, rigid outer region consisting of the crust and uppermost mantle where materials are well below the melting point temperature. The thickness of the lithosphere is variable: up to ~70 km thick beneath ocean basins but thicker beneath continents and especially beneath mountain ranges The rigid lithosphere is broken up into a number of pieces of varying sizes called plates. The lithospheric plates, because of their relatively low density, "float" on the weaker, partially molten asthenosphere. The lithosphere includes both the crust and the uppermost mantle.
Describe the composition of the mantle and crust and the minerals that are commonly found there.
The mantle is composed mostly of Iron (Fe), Magnesium (Mg), Silicon (Si), and Oxygen (O). In other words, the mantle is an iron magnesium silicate, i.e., the mineral olivine. Minerals like olivine that are rich in iron and magnesium are said to be mafic because they appear dark in color. The composition of the crust is more variable than that of the mantle, but still only 12 elements occur in the continental crust in amounts greater than 0.1 percent by weight. These 12 elements make up 99.23 percent of the crustal mass. The crust, therefore, is constructed mostly of a limited number of minerals. Approximately 4,000 minerals have been identified, but only about 30 are commonly encountered. The crust is a sodium potassium calcium aluminosilicate, i.e., feldspar. Minerals like feldspar that contain Na, K, Ca, and Al are said to be felsic because they appear light in color.
Mesosphere
The mesosphere is the deep part of the mantle where rocks again rigid despite high temperature due to high confining pressure (670-2890 km depth).
Magnetic Field
The molten iron in the Earth' outer core combined with the Earth's rotation generates a magnetic field. Molten iron in the outer core flows around the solid inner core because of Earth's rotation. The flow generates an electrical current, in turn creating a magnetic field. Earth's magnetic field resembles that of a simple bar magnetic with two poles of opposite polarity. Because the magnetic field is generated by Earth's rotation, the magnetic poles are within a few degrees of the rotational (geographic) poles. The origin of the Earth's magnetic field is not completely understood, but is thought to be associated with electrical currents produced by rotation in the spinning liquid outer core made of iron and nickel. The liquid iron in the outer core is also in motion due to convection, changes in convective currents may account for the observed variability in the strength and polarity of Earth's magnetic field.
Oceanic Crust
The oceanic crust is more dense and thinner, with a chemical composition similar to the rock type basalt (made of the elements Si, O, Al, Ca, Mg, Fe). Oceanic crust is youngest at the ridge and gets older with increasing distance from the ridge.
Subduction and Subduction Zone
The origin of earthquakes becomes deeper along one side of ocean trenches with increasing distance from the trench. This marks the descent of old oceanic crust into the mantle as it is destroyed. This process is known as subduction and the places where it occurs are called subduction zones.
Rock Cycle
The rock cycle describes all the processes by which rock is formed, transported, decomposed, and reformed. Active volcanoes produce igneous rocks. Mountain ranges rise as a result of plate tectonics. Weathering and erosion change the surface of the solid Earth. The sediment is buried and compacted, eventually becoming sedimentary rock. Deeper burial turns sedimentary rock into metamorphic rock. Even deeper burial may cause some of the metamorphic rock to melt, forming magma from which new igneous rock will form.
Scientific Method
The scientific method is the way researchers work collectively over time to develop an accurate, reliable, and unbiased explanation of the world around us. Observe, hypothesize, predict, test, modify.
Geology
The study of the Earth and in particular the materials composing the Earth, the structure of those materials, and processes acting on the Earth.
Identify the three types of plate boundaries and describe the major geologic and tectonic processes occurring at each.
There are divergent, convergent, and transform plate boundaries. Divergent plate boundaries occur where plates are being pulled apart. At divergent plate boundaries new oceanic crust is created as the two plates pull away from each other. Divergent plates generally can cause extensional stress, shallow earthquakes, and basaltic volcanism. Examples of divergent plate boundaries are mid ocean ridges, like the Mid-Atlantic Ridge. When a continent is being pulled apart a new divergent boundary, known as a continental rift valley is made. These continental rift valleys are the earliest stage in a new ocean basin occurring which happens when continental plates split apart and new oceanic crust grows between them. Convergent plate boundaries occur when plates are moving together and colliding. During ocean-ocean plate convergence the older oceanic crust is subducted underneath the newer and it created a trench. During ocean-continent plate convergence oceanic crust is also subducted under the continent and destroyed. This can also create a trench. During continent-continent plate convergence both plates are too light to be subducted so that can create mountain ranges and high plateaus in these areas. Transform plate boundaries occur when two plates are sliding past each other. This is marked by a system of faults. When these plates move it can create friction, so that causes plates to generally build up tension so when it builds to much the plates lurch past each other causing earthquakes. The stress and movements can cause edges of the plates to crumble on both sides.
Describe the earth's inner structure, in terms of both general composition (major chemical elements) and physical properties (i.e., solid or liquid, strong or weak).
There are more than 100 naturally occurring chemical elements. Yet the earth is mostly (~90%) made of only four: iron, oxygen, silicon, and magnesium. The curst, mantle, and core have different densities due to their different chemical compositions: the crust has a density of 2.2 - 2.8 gm/cm3, while the mantle has a density of 3.3-5.8 gm/cm3 and the core 10.7 gm/cm3. The strength of earth materials is a function of their temperature relative to their melting point. Materials close to or above their melting point temperature will be weak or molten. Melting point is a function of both temperature and pressure: the higher the confining pressure (the greater the depth below the surface) the higher the melting point. The inner structure of the Earth consists of layers with different physical properties: the lithosphere, asthenosphere, mesosphere, and the outer and inner core.
Tsunami
Tsunami are seismic sea waves caused by abrupt vertical displacement of the water column. Tsunami are most commonly produced by underwater earthquakes as in the case of the December 2004 tsunami in the Indian Ocean.
Ultramafic
Ultramafic igneous rocks are composed of mostly one mineral: olivine.
Van der Walls Bond
Van der Waals bonds are weak secondary attraction between certain molecules formed by transferring electrons. Van der Waals bonds are much weaker than ionic, covalent, or metallic bonding.
Craton
Very ancient rock that make up the cores of continents. Exactly how cratons formed is still debated.
Viscosity
Viscosity describes a magma's resistance to flow and is determined by silica content (composition) and temperature. Viscosity increases with increasing silica content but decreases with increasing temperature. Viscosity in turn affects the dissolved gas content of a magma. Higher viscosity magmas tend to trap more dissolved gases. Rhyolitic magma (70% silica) is always more viscous than basaltic magma (50% silica). Andesitic magma has a viscosity that is intermediate between the two (60% silica). The viscosity of the magma controls the style of eruption.
Explain the different hazards associated with volcanic eruptions, and provide specific examples of past volcanic eruptions that produced such effects.
Volcanic gases Pyroclastic flows Ash Fall Lahars Lava flows Tsunami Climate Change
Hot Spot and Tracks
Volcanism is usually associated with plate boundaries. However, some volcanic centers are located in the middle of a plate. Such centers are called hot spots and have a magma source in the deep mantle, perhaps extending all the way to the core boundary. Because the magma source is below the lithosphere, it does not move with the plate. Instead a chain of volcanoes called a hot spot track is produced as the plate moves over the stationary hot spot. The Hawaiian Islands are an excellent example of a hot spot track. The Yellowstone hotspot is the world's only hot spot beneath a continent and is responsible for Yellowstone National park's famous geysers and hot springs as well as three enormous volcanic eruptions in the last two million years. A hot spot is an area of deep mantle upwelling that is independent of plate boundaries.
Pillow Basalt
When basaltic magma erupts under the ocean, seawater cools it so rapidly that pillow-shaped masses of basalt, ranging from a few centimeters to a meter or more in greatest dimension form.
Tuff
When bomb-sized tephra are transformed into a rock they are called agglomerates. They are called tuffs when particles are either lapilli or ash.
Subduction zones were discovered when?
When it was noticed that deep earthquakes are found only near ocean trenches, and that earthqauakes increase in depth with distance from the trench
Tectonic Cycle
When magma rises from deep in the mantle, it forms new oceanic crust at mid-ocean ridges. As oceanic crust ages, it cools and is eventually forced back down into the mantle, a process known as subduction. As old oceanic crust sinks into the mantle, it melts, producing magma. Hot magma rises towards the surface, where it may introduce into the crust or be erupted onto the surface by volcanoes, forming igneous rocks. Mama may also rise a mid -ocean ridges, forming new oceanic crust and completing the cycle.
Apparent Polar Wander
When the magnetic direction and inclination of rocks of different ages from the same continent are plotted on the map, they appear to indicate that the magnetic poles have wandered great distances over time. Furthermore, rocks from different continents appear to show the magnetic poles taking different paths at the same time.
Carbonate
contain carbonate ion, CO32-
Halide
contain halogens such as chloride
Oxide
contain oxygen atoms not bonded to carbon or silicon
Conchoidal Fracture
he most common fracture type is conchoidal. This is a smoothly curved fracture that is familiar to people who have examined broken glass. Quartz has this fracture type and almost all specimens that have been broken, demonstrate this fracture type very well.
Tectonic plates of rigid and brittle __________ move over a softer and ductile ___________ below.
lithosphere, asthenosphere
Which group of igneous rocks is all extrusive?
pumice, basalt, andesite
Native Element
single element, such as copper