Geoscience Midterm Ecore

Lithosphere

Crust and Upper mantle (behavers in a rigid manner while containing very little silica or oxygen)

Mid-Ocean Ridges What composition should be expected?

-Products of this volcanism over 70% of Earth's surface -Divergent - Basaltic Lava, Pillow Basalts

Definite Chemical Composition:

1 or more elements make up the chemical formula - Determines crystalline structure - Determines properties of minerals Ex: Garnet (X3Y2Si3O12)

Naturally Occurring:

1 or more of the 92 naturally occuring elements - Formed by geologic processes: --Crystallized from molten material --Precipitated from a solution --Produced by living organisms

Developing Plate Tectonic Theory Alfred Wegener

1915: proprosed the idea of continental drift based on an abundance of evidence

Harry Hess - Finishing What Wegener Started

1960: Magma rises up at mid-ocean ridges, forming basaltic oceanic crust

Intermediate

55 to 65 % silica, ex diorite, even mixture andesites, look grey.

When was the first star born

800 million years after the big bang

Oceanic-Oceanic Convergence - Plate movement: - Geologic features: - Real-world example:

2 oceanic plates come together Which plate will subduct? Old= denser, island arc, accretionary prism, oceanic trench, back-arc basin, Western Pacific, Japan make up volacanic arch

Mafic

45 to 55 percent silica in them, iron and mag rich, why the color is dark. Basalts and gab brose ex

Felsic

> 65% SiO2, ex: quartz and feldspars few ferromagnesian minerals

Decompression Melting

A decrease in pressure can trigger melting if the rock remains hot Occurs as hot mantle rises slowly.

Porphyroblast

A porphyroblast is a large mineral crystal with a finer grain groundmass. Sound familiar. This is very similar to the igneous phenocryst, that gives igneous rocks a porphyritic texture. These textures are specific to the rock types they are found in, which is why we make a distinction in their names. In this image, the large red splotches are garnet pporphyroblasts within a finer grained silica rich matrix. Garnett is a pretty common porphyroblast in metamorphic rocks. You can often see you euhedral crystals in phyllites and schists.

Lava Domes

Accumulation of Si-rich volcanic rock and obsidian - Can be highly unstable.

Active vs. Dormant vs. Extinct

Active: erupting, has erupted recently, likely to erupt (Kilauea, Hawaii) Dormant: not erupted for hundreds/ thousands of years but might erupt (Mt. Fuji, Japan) Extinct: will never erupt again (Devil's Tower, Wyoming)

The Birth of Stars

All matter has gravitational attraction

beds

All sedimentary rocks form in layers or beds on top of underlying basement rock

Gneiss: o Grain size: o Protolith: o P-T conditions: o Other:

Alternating layers of light & dark colored minerals They can form from other igneous or sedimentary rocks that are comprised of both silica-rich and iron-rich minerals. The temperatures and pressures are so high that we get a full separation of mafic and felsic minerals shales as the rest of the foliated rocks do. They can form from other igneous or sedimentary rocks that are comprised of both silica-rich and iron-rich minerals. It has been my experience as a metamorphic petrologist that a significant amount of gneiss forms from granite. And I think that is the easiest protolith to remember. Gneiss is a metamorphosed granite.

Proving Continental Drift and Seafloor Spreading: Paleomagnetism

An Fe-rich mineral will crystallize to align with magnetic north. Magnetic north changes over geologic time. Ricks record the position of magnetic north-paleomagnetism

Graded Beds

As all sediment settles, larger grains will settle first, followed by progressively finer grains. This creates a graded bed, with distinctively large grains on the bottom and fine grains on the top. Multiple turbidity currents will travel through submarine canyons. This will create a graded bedding sequence and burial of older sediments will cause compaction, cementation, and ultimately lithification. What we see in a graded sequence of sedimentary rocks is the formation of a conglomerate overlain by a sandstone, then possibly a siltstone and finally a shale.

Phyllite: o Grain size: o Protolith: o P-T conditions: o Other:

As new minerals are forming the conditions are right to form fine-grained mica, which will give phyllite a little bit of a sheen shale, or something that is full of clay minerals, like slate high enough to cause neocrysstallization and growth of white mica Slate is dull its appearance, but phyllite will have a little bit of a reflective sheen when tilted and turned on the light. Due to the softness and fine-grained nature of the Mica, the layers or foliation, a phyllite can sometimes be lost. And it's not as distinctive as it is in slate or schist.

Pyroclastic Debris (Tephra)

Ash- rock particles that have been pulverized into dust fine enough to be carried along wind currents It is most often seen with eruptions produced by andesitic to rhyolitic compositions, because of the explosive nature of these eruptions. Eruptions of basaltic material don't produce ash because the melt is so willing to come out of the vent. lapilli- tiny rock particles larger than ash, but smaller than the larger chunks of rocks usually seen. Lava fountains are common with basaltic flows. As the lava spews out, small rock fragments are caught up in it and then rain down to create a show. volcanic bombs- basaltic material will have gas trapped in it that rapidly decompresses when exposed at the surface, causing explosions around the volcanic vent. These are not large scale as the explosion scene with andesitic to rhyolitic eruptions. But they are large enough to shoot larger pieces of rock from the volcanic crater. Andesitic/ Rhyolitic eruptions- pyroclastic flows

Continental Rifts

Basaltic fissure eruptions, development of cinder cones, & explosive rhyolitic volcanism

Lava Flows

Basaltic: Low Si-content, high temperature- thin, runny magma Andesitic/Rhyolitic: Higher Si-content, lower temperature- thicker, sticker

Shield Volcanoes Type of eruption: Lava composition:

Broad, gentle slopes Example: Mauna Loa/ Kilauea Effusive eruption- low viscosity lava spills/fountains steadily from a vent or fissure Basaltic composition- flows far, fast

Marble: o Grain size: o Protolith: o P-T conditions: o Other:

Calcite, fossils, & cemet recrystallizes to form larger interlocking calcite crystals Limestone High PT conditions Can't scratch glass, reacts with dilute hydrochloric acid

Igneous textures

Can see texture.

Organic

Carbon-rich relicts of plants/ organisms (coal)

Dolostone

Carbonate: CaMg[CO3]2 - equal amounts of Ca and Mg Reaction between calcite & Mg- bearing groundwater.

A sedimentary rock is a rock that is formed at or near the surface. What are the 4 processes that can form a sedimentary rock?

Cementing together loose clasts produced by weathering of pre-existing rock. Growth of shell mounds/cementation of shell fragments Accumulation/ alteration of organic matter Precipitation of minerals from surface water solutions

River

Changing energy as it moves downstream- gravel, sand, silt, mud.

Delta

Changing energy causes sediment loads to be dumped.

Travertine

Chemical limestone

Chemical Weathering

Chemical reactions alter or destroy minerals.

The Barrovian Sequence:

Chlorite, for instance, forms at low temperatures and pressures. Chlorite is a green Mica mineral that may give a gray slate, a greenish tinge, or give a phyllite it's sheen. No matter what the protolith is, chlorite forums at the lowest pressure temperature conditions. Garnett is also formed from both protoliths. It forms at the upper end of the intermediate grade and will continue to form in high-grade rocks. This means that when we see garnet, the rock may be intermediate to high grade. When garnet appears in a schist, we know the rock is an intermediate grade rock because muscovite and biotite don't really form beyond the upper end of the intermediate grade pressure temperature conditions. Some minerals are better at indicating metamorphic grade than others. Quartz and feldspar will appear in any rock of any grade, though they may look different at different grades. However, minerals such as staurolite, kyanite, and sillimanite are great indicators of pressure temperature conditions, because they form in a very narrow window of pressures and temperatures. In fact, when pressure conditions become too high, kyanite experiences a phase change and becomes sillimanite. Both minerals or aluminosilicates with different crystalline structures. Muscovite and biotite span across both the low and intermediate grades, but their textures vary. So while they themselves may not be as good of an indicator, their textures may indicate what grade the rock formed at. Finer grained micas form phyllites which are low to intermediate grade rocks, while coarser grain micas form schists. From this, we can conclude that mica will increase in grain size with increasing metamorphic grade. Therefore, a coarse-grained schist will be an intermediate grade. We've established that certain rocks form at certain metamorphic grades, and those rocks will have a distinctive mineral assemblage.

Streak

Color of the powder produced by a mineral when it is scratched across an unglazed porcelain called a streak plate Hematite- blood red or a reddish brown streak Sphalerite- yellow and smells like rotten eggs Pyrite- dark gray to black streak

How are igneous rocks described?

Color, Texture (gain size) (noticeable grains vs non-noticeable Dark color indicates that the mineral of a rock is more iron and magnesium rich than those in granite. Focus mainly on mineral composition and texture. Color, Texture (gain size) (noticeable grains vs non-noticeable Dark color indicates that the mineral of a rock is more iron and magnesium rich than those in granite. Focus mainly on mineral composition and texture.

How are igneous rocks classified?

Composition and texture, however each environment, environmental setting where melt is produced and/ or cools and crystallizes is unique, making igneous rocks unique.

Convergent o Type of stress: o How do the plates move?

Compressional, Towards each other

Contact Metamorphism

Cooler country rock is heated and metamorphosed as hot magma & hydrothermal fluids rise through the crust

Chemical Sedimentary Rocks

Crystalline texture - Original precipitation - Recrystallization

Fragmental Texture

Debris welded together during an eruption. - Various grain sizes

What does the magnetic field do for the planet?

Deflects solar winds which eventually created the Earth's atmosphere

What determines which plate will subduct

Density determines which plate will subduct

Mantle Convection

Density-driven, can't explain geometry seen at plate boundaries & differing plate motion velocities, not the only thing causing plates move

Factors to magma cooling

Depth of intrusion Shape and size of magma body Presence of circulating groundwater

What happens when a star runs out of fuel?

Dies, collaspsing on itself (gravitational compression), then explodes into a supernova

Gas Release

Dissolved gases in magma: H2O, CO2, SO2 Up to 9% of magma can be gas Andesitic/rhyolitic magmas tend to trap more gases.

How is stress different from pressure?

Does not happen in all directions equally like pressure does

What is the evidence for why mantle convection is not the only process involved with plate movement

Doesn't explain the geometry seen at plate boundaries or why plates move at different velocities.

Slab-Pull

Downgoing plates are more dense than the asthenosphere Willingly sinks, pulling the rest of the plate

Types of Melt

Dry melts: no volatiles Wet melts: have volatiles - Volatiles erupt as gases.

Stellar nucleosynthesis

During the life cycle of a star, heavier elements such as Iron, Nickel, Silica, Oxygen form as a byproduct of the fusion reaction in stars

What generates Earth's magnetic field?

Earth's magnetic field is genetrated from hot spinning metals caused by the Earth's inner core (friction between inner and outer core)

Supervolcanoes

Eruptions eject over 1000 km^3 of debris -Largest known: 73,000 BCE, Indonesia- 2800 km^3 of debris Caldera forms Lake Toba

Alluvial Fan

Fast-moving, high energy stream deposits its sediment load onto a plain due to an immediate change in velocity - Breccia, conglomerate, arkose

Marine Magnetic Anomalies/Polarity Reversals

Fe-rich mineraks making up oceanic crust record magnetic anomalies Precise "striping" of the seafloor provides indisputable evidence of seafloor spreading

How does color help to determine composition in igneous rocks?

Felsic rocks are lighter in color because of their silica content. Mafic rocks tend to be darker in color due to their ferromagnesian or silica poor content.

Hornfels: o Grain size: o Protolith: o P-T conditions: o Other:

Fine-grained with variable composition Various proliths- fine-grained rocks such as mudstone or volcanic rock Variable P-T conditions Garbage can rock

Wegener's Evidence

Fit of the Continents, Glacial Data, and Distributions of Fossils

Flood Basalts

Flood basalts don't really fit into any category we've discussed thus far. They are produced by an extraordinary amount of low viscosity lava erupting out of fissures, then spreads out into vast sheets. When I say an extraordinary amount, I mean a lot. The Columbia River plateau is the result of an effusive fissure eruption that occurred about 15 million years ago. During this eruption event, 220 thousand square kilometers were covered in 3.5-kilometer-thick basalts. On an even larger scale, and something that completely changed Earth's history, was the eruption of the Siberian Traps. This happened 250 million years ago and was an eruption event that lasted 2 million years. One continuous eruption for 2 million years. I can't emphasize how much material that is and how extraordinary it is for a single eruption event to last for 2 million years. This event is thought to be responsible for the largest mass extinction event on the plane.

What is Geology?

Geology is the study of the Earth

How does melt form?

Geothermal gradient Pressure is also a factor. - The mantle is extremely hot, but also solid -Melt forms under a certain set of conditions

What allows us to have an atmosphere?

Gravity

Crystalline Texture

Grew in an interlocking framework, leaving no open space.

Agents of Metamorphism • Increasing Temperature Associated metamorphic processes: o Metamorphic rocks form in what temperature range?

Heat causes atoms to vibrate rapidly, stretching/bending/breaking their bonds -Form new bonds with other atoms recrystallization/ neocyrstallization 250 degree C and 850 degree C

How does mantle convection work?

Heating material gives it a different density, which creates a convection motion through the heating of the Earth

High viscosity magmas

High SiO2 content (felsic composition) = moves slowly

Mountain Stream

High energy; can carry large clasts: boulder, cobble, & pebble deposited.

Cleavage & Fracture

How the mineral breaks Comes down to the crystalline structure of the mineral If a mineral does not break along any particular plane of weakness = fracture Fracture is irregular, but may occasionally break in this disk like manner, like glass- conchiodal fracture Breaks along the regular plane of weakness = clevage One directional clevage (basal clevage) = one plane of weakness and peels into thin sheets More than one plane of weakness= clevage planes will intersect one another Pyroxenes - two directions at 90 degree angles Amph - two directions of clevage not at 90 degree (60, 120) Ideal example of cubic cleavage: 3 clevage planes all at 90 degrees The mineral can break on any plane parallel to its set clevage planes 3 planes of cleavage not at 90 degrees= rhombic clevage

Hydrosphere/Cryosphere

Hydrosphere- comprised of all of the water on the planet Cryosphere- comprised of all of the frozen water on the planet

Theory

Hypothesis that cannot be proven false after an abundance of testing

polar wander path

If the continent is in a fixed position, the magnetic pole must move If the pole is fixed, the continent must be drifting

The Rock Cycle, an Introduction

Igneous Rocks form from the cooling and crystallization of melts. Sediment forms from the breakdown of pre-existing rock belonging to any of the rock types and lithifies into sedimentary rock. Metamorphic rocks form when any pre-existing rock is subjected to heat, pressure, and potentially chemically reactive fluids that ultimately change the mineral composition of the rock

Intrusive settings/bodies

Igneous intrusions dikes- vertical igneous intrusions that cut across country rock in a vertical manner sills- Typically occur in sedimentary rocks that were magma find space between sedimentary layers. Dikes and sills range in size depending on how long they are fed from the orginal magma chamber. Fine grained because they cool relatively quickly given the size and shape of the magma body, and due the the fact they are surrounded by cooler country rock. laccolith- similar to sills in that they extend laterally, parallel to the bedding of the country rock. However, laccoliths may build up so that a blister of magma forums instead of a thin layer. It is simply a bigger magma body., plutons- much larger ignerous bodies. They cool and crystallize at depth. Plutons are generally magma chambers that have risen to a certain point in the crust and cooled over a long period of time. Because of the slow cooling, plutonic rocks are typically coarse-grained. Over time, these bodies may be exposed at the surface. EX Stone Mountain Batholiths- form in the same manner as plutons and have the same characteristics, except they are much larger diapirs- the path of rising magma. Once a volcano is formed, they are referred to as diapirs. The picture along the pictures has cooled and crystallized over a long period of time, the crust may experience weathering, erosion and uplift that forces a body of igneous rock that formed at some depth to the surface. Therefore, when we seem at the surface, we say they are exposed intrusive bodies.

Minerals vs. Gemstones

In summary, we can distinguish between a mineral and a gemstone based on their composition and usage in jewelry making. Minerals are typically crystalline; if a gemstone has the crystalline composition, it's regarded as a mineral. If a mineral is regarded as rare and exceptionally beautiful, we refer to it as a gemstone. The same applies to rocks.

Terrestrial planets

Inner planets (Mercury) with thin layer of gas to make up the atmosphere

How is a metamorphic rock different from an igneous rock?

Iron-rich minerals crystallize at a higher temperature and pressure

How did Earth's Moon form?

Just before the Earth had fully differentiated, a Mars-sized protoplant (to be Moon) slammed into the Earth. Due to Earth gravational pull, the debris stayed close to Earth and became the Moon.

Debris Flows and Lahars

Lahars form when ash-rich debris becomes very wet Debris flows travel downslope rapidly Form layers of volcanic debris in ashy mud.

• Stratovolcanoes: (Composite volcanoes) o Type of eruption: o Lava composition:

Large, steep-sided volcanoes consisting of interlayered lava, tephra, and volcaniclastic debris Ex: Mt. Fuji, Japan (most of the volcanoes you think of) Explosive eruption- pyroclastic debris blasts forcefully into the air Andesitic/ rhyolitic composition- lava does not flow far - A lot of gas and pressure builds over time..

Shallow-Marine Carbonates

Limestone= lithified reef

Ridge-Push

Lithosphere at mid-ocean ridges lies at a higher elevation Gravity causes the elevated lithosphere at the ridge-axis to push lithosphere away from the ridge

Special Locations: Hot Spots

Locations where volcanism and tectonic activity may occir within a plate, instead of at a plate boundary Ex: Hawaii

Lake (Lacustrine)

Low energy; mud particles (form shales)

What are the 3 classes of metamorphic grade?

Low, Intermediate, and High

Asthenosphere

Lower mantle, outer core, and inner core. Similar composition to the Upper Mantle but more of a plasticky solid than a rigid solid.

What determines magma composition?

Magma composition is determined by source rock composition Also Partial melting: part of an original rock melts Assimilation: incorporating constituents from surrounding country rock.

Movement of Magma

Magma rises upward, away from the site of melting Density driven process: molten rock is less dense than the surrounding solid rock, causing it to rise.

How are magmas classified?

Magmas are classified by their SiO2 composition.

silicate mineral group

Make up 95% if continental crust and 100% of oceanic crust The base of all sillicates is the silicon-oxygen tetrahedron Isolated tetrahedra do not bond with other silica tetrahedra in a particular manner. Ex: Olivine and garnet Single chain silicates are bonded tetrhedra with one corner bonded with another. The pyroxenes, including the minerals augite, are single chain silicates. Rember that the pyroxenes have two directions of clevage at 90 degrees. This is due in part to the single chain structure of the tertahedra. In contrast, are the double chains of tetrahedra that are the amohiboless, including the mineral hornblended. This double connection between tetrahedra, it gives the amphiboles a different angle of intersecting clevage planes from the pyroxenes Sometimes the tetrahedra bond in such a way that they form sheets.The sheets themselves are bonded similarly to how carbon sheets are bonded in graphite, in that the sheets are layered. The bonds between the tetrahedra are strong, but the bonds between the sheets are weak.This type of bonding produces the sheet silicates- the mica group. Muscovite and biotite are both part of the mica group, dustinguished from one another by color. Some of the strongest bonds between tertahedra occur in quartz and the feldspars. The tetrahedra create a 3-D framwoek that gives both quartz in all of the feldspars are relatively high hardness. The reason beind the strengthin bonding is that all four corners of the tetrahedra are shared with adjacent tetrahedra.

What 2 factors influence an object's gravitational attraction

Mass and Distance

Pegmatitic Texture

Masses of very large crystals Very slow crystallization

Regional Metamorphism

Material is buried causing increased temperature, pressure, & stress

Rates of Plate Motion

Measured in Cm/year

Amphibolite: o Grain size: o Protolith: o P-T conditions: o Other:

Medium-coarse grained Mafic igneous rocks, greywacke (sandstone) Med-high P-T conditions Dominated by hornblende & plagioclase May be foliated

Lava

Melt erupted onto the surface

Magma

Melt underground

Luster

Metallic- with metalizic bonds, electrons move around vs Non Metallic- not enough metalic elemnts or metalitic properities Viteous vs Glassy Earthy and dull or waxy and pearly

What aspects of the environment are changed in order for metamorphism to occur?

Metamorphic rocks often contain new minerals and textures from their protolith. The protolith is the parent rock or the pre-existing rock. Temperature and pressure dominate the conversation around metamorphic rocks. But the reality is that there are a few different agents of metamorphism. Temperature and pressure are the most obvious because they are responsible for creating the environmental conditions rocks form under. However, pre-existing rocks may also change due to added stress in the environment, such as what we see along fault zones.

Migmatite

Migmatites form under extremely high temperatures. Remember, different minerals have different melting points. At high temperatures, somewhere around 650 degrees Celsius or 700 degrees Celsius, the gneiss begins to melt. Specifically the felsic minerals within the gneiss melt. The mafic layers have a higher melting temperature, so they remain solid, while the felsic layers become liquid. This means that the quartz and feldspar rich materials are mobile and create this squiggly effect within the gneiss.

How do galaxies form?

Nebula material coming together in an accretionary disk (hot in the center while colder on the outside and spinning)

Metamorphic facies

Mineral assemblages indicative of a certain range of PT conditions are referred to as metamorphic facies. Metamorphic facies help us to better define the conditions under which the rock formed. This is a little more precise than just listing metamorphic grade. Because the metamorphic grade can range between low to intermediate, and intermediate to high. A facies is a more narrow range of PT conditions. And so by listing the facies, we get a better idea of where in the crust the rock formed and under what conditions. We also know that some facies are particular to specific environments. Lucius facies rocks form in the increase in the accretionary prism of a subduction zone. The upper regions of a subduction zone dominated by intense pressure without as much heat from burial. Likewise, hornfels is a temperature dominated facies without a lot of intense pressure.

Human Time vs. Geologic Time

Much longer than human time scales (millons of years instead of hundreds) Ma- millions of years ago Ga- billions of years ago Precambrian Eon ( 4 billion years, most of Earth's history)- Hadean, Archean, and Proterozoic eons Phanerzoic Eon- 3 segments Paleozoic- major diversification of life Mesozoic- Dinosaurs Cenozoic- Creation of mammals (now!)

Color

Not an dianostic properity Olivin is olive green Azurite- bright dark blue Feldspars Potassium feldspar is salmon pink Sulfur will always be yellow Hematite (earthy) vs Hematite (specular)

Angularity/Sphericity

Not travel far/ distance

After the Big Bang, matter accumulated in clumps. - What is responsible for igniting a star?

Nuclear fisson of Hydrogen and Helium

Extrusive settings

Occur anywhere a volcano erupts. All lava flows and pyroclastic debris are extrusive in origin. Lava flows will travel across the land surface and cool relatively quickly in their paths. Pyroclastic debris will be deposited or settle out of the atmosphere to create thick or thin beds of volcanic ejecta.

Oceanic-Continental Convergence - Plate movement: - Geologic features: - Real-world example:

Oceanic crust subducts beneath a continental crust, Continental volcanic arc, accretionary prism, oceanic trench, mountain belt, Andes Mountains on western edge of SA

Imbrication

One unique sedimentary structure that is almost exclusively found in conglomerates as something called imbrication. Imbrication occurs when flow is strong enough to position large clasts such as pebbles and cobbles in a stacked arrangement. All of the clasts are tilted in the same direction, the flow direction. This means the imbrication of clast can help us determine flow direction of the fluid that deposited the sediment.

Organic Sedimentary Rocks

Organic matter- no hard parts - Forms from plants buried in an anoxic environment (swamps) - Oil shale: clay with 15-75% organic material (kerogen)

Biochemical Sedimentary Rocks

Organisms extract dissolved ions from seawater to make shells. - Die & shells are deposited on the seafloor, then lithified - CaCO3 -> What mineral? -Forms limestone - Fossiliferous, chalks, massive Biochemical chert forms from Si-secreting organisms that accumulate into a siliceous ooze on the seafloor. - Deep water - Microcrystalline quartz

What is the difference between the outer core and the inner core?

Outer core is liquid while the inner core is solid

Jovian planets

Outer planets (Neptune) with thicker layers of atmphore

The Crust

Outermost layer of the Earth, as well as the thinnest with the highest concentration of lighter elements like Oxygen and Silicon. Crust varies chemically too with the oceanic and continental crust. The oceanic crust is more iron-rich which create darker rocks while the continental crust is more silica-rich which create lighter rocks.

How was the atmosphere created?

Outgassing from volcanoes erupting during Earth's early days

Protolith

Parent rock/ pre-existing rock

soil

Physical & chemical interaction with organic material, rainwater, & organisms at or just below Earth's surface over time

Metamorphic Grade

Physical conditions under which MMM takes place varies - Intensity varies Ex: rocks carried to a greater depth undergo more intense MMM than rocks closer to the surface - MMC grade indicates intensity

Cinder Cone Volcanoes

Piles of basaltic lapilli and blocks - 1 eruption event: can last for days or years.

Internal Processes Example

Plate movement causes mountain building, volcanism, earthquakes, etc.

Sorting

Poor sorted- Variety of grain, not far Well sorted- same grain size, far.

Hypothesis

Possible explain for observation

Vesicular Texture

Rapidly cooling lavas can trap gas bubbles remain as open holes in the solidified rocks as vesicles Pumice: felsic, glassy rock with abundant vesicles Scoria: mafic, glassy rock with abundant vesicles.

What materials make up solar systems?

Primordial gases leftover from the Big Bang inside of dead stars.

Evaporites

Products of saltwater evaporation (supersaturated) Gypsum: 80% of the water evaporates. Halite: 90% of the water evaporates

Quartzite: o Grain size: o Protolith: o P-T conditions: o Other:

Quartz grains recrystallize into larger grains Clean quartz sandstone High PT conditions Can scratch glass, wont react with dilute hydrochloric acid

How do we know what Earth's structure is?

Reflection and refraction of waves at different densities caused by Earthquakes show what the interior of the Earth is made up of

Hardness

Relative ability of a mineral to resist scratching >2.5 can be stratched by fingernail >5.5 Scrtach by glass plate Diamond = 10 Talc= 1

Convergent Boundaries

Remember that at convergent boundaries, volcanism only occurs where subduction occurs. That means we see volcanism at oceanic- oceanic boundaries as well as that oceanic- continental boundaries. The compositions at each are more of a range. At island arcs, we see a basaltic andesitic range because most of the material is iron rich and silica poor. We give it the range of basaltic andesitic, instead of saying it is purely basaltic. Because as the magma rises through the crust, silica rich materials may be assimilated into the magma to alter the composition. This means that basalts and iron-rich and andesites may be produced an island arc. At continental volcanic arcs, we see a range of andesitic to rhyolitic compositions. Andesites are produced by the iron-rich materials from the subducting oceanic plate. But silica rich material is incorporated into the melt as it rises through continental crust. With each composition, a different type of volcano maybe produced. At island arcs shield volcanoes may be produced, but stratovolcanoes are also common. The island arc in Alaska, for example, is made up primarily of stratovolcanoes. This is the andesitic composition causing the lava flows to build up around the vent instead of flowing. At continental arcs, stratovolcanoes are present.

Glassy Texture

Result if extremely rapid cooling No mineral grains present SiO2 glass: Obsidian

Heat Transfer

Rising hot magma from the mantle brings heat with it that melts crustal rock Volcanic gasses mix with the atmosphere, volcanic eruption, extrusion of lava, magma differenation in magma reservoirs, Intrusion, stagnation, crystallization, intrusion, underplating, magma rises, partial melting.

Andesitic/Rhyolitic vs. Basaltic

Same as Intermediate/ Felsic or Mafic Si rich vs Si poor

How were Wegener's ideas received by other scientists at the time? Why?

Scientist of the 1930s believed Wegner was wrong. Wegner didnt have the "how" or "why" Could not explain how continental crust could move through denser oceanic crust. Could not explain why the plates would move at all

Accretionary prism -

Sediments may be scraped off of the down-going plate like a bulldozer scrapes sediment off the landscape on a construction site. This creates a wedge of sediment in the suduction zone, that may build up enough to slow the sinking plate down or clog up the suduction zone alltogether. Can create island arcs or micro continents

Transform o Type of stress: o How do the plates move? o Geologic features: o Real-world example:

Shear, Plates move past each other, lateral movement, "step-over" daultiing at mid-ocean ridges; lateral movement, San Andreas Fault System

What determines the behavior of lava flow?

Si content determines behavior of lava flow.

Chemically Precipitated Chert

Si dissolves in groundwater & precipitates at microcrystalline quartz

Ultramafic

Silica poor-rarely seen at the surface <45% SiO2, rich in iron and magnesium (peridotite and dunnite)- olivine, green or black.

How are igneous rocks formed?

Solidifying melt. Melt can form deep in the mantle and rise to the surface. Or it can form from surface rocks that are buried to such a depth, they form a completely new melt. Any rock formed by the solidification of a melt.

Parts of a Volcano

Something I talk about a lot is the volcanic vent, labeled as three in this diagram. The vent is basically a conduit pipe that connects the top of the volcano to the underlying magma chamber. The typical triangle shaped volcano is built up around this conduit. When an eruption happens, it is what is called a crater eruption because the material is blasted out of the crater at the top of the volcanic peak. Usually, but there are always exceptions. However, this is not the only type of eruption there is. Particularly at continental rift zones, we may see something called a fissure eruption. Fissures are large cracks that open up across the land surface in a geologically active area. When a fissure eruption happens, lava spews out in a sort of curtain along the fisher. Basaltic material is the only type of material that would have a low enough viscosity to do this. So, you will rarely see a fissure eruption with silica rich compositions. Again, there are one or two volcanoes on the planet that like to be the exception. There is a difference between a crater and a caldera on a volcano. As the underlying magma chamber fills, the ground above swells and fractures. During the eruption, as the magma chamber drains, the portion of the volcano around the vent collapses, creating a crater. Once the magma chamber is empty and the eruption event is over, overlying material will collapse in on itself because there is no longer magma beneath it to hold it up. This creates a caldera. So, a crater forms during an eruption and a caldera form after an eruption. Over a period of time, the magma chamber will begin to fill again and burp out material that will build up a smaller volcano around the vent within the caldera.

Divergent o Type of stress: o How do the plates move? o Geologic feature(s): o Real-world example:

Tensional stress, Away from each other, The lithopshere is thinned and weakened by hot mantle material rising up, and pushhing through the crust, Mid-ocean ridge, rift valleys on young divergent boundaries, Middle of ocean basins and form mid-ocean ridges, East Pacific Rise, Atlantic Basan

The Big Bang Theory

The Big Bang Theory explains the universe expanding from a central point. An explosion happed around 13.8 billon years ago and since then the universe has been expanding.

What does the Solar Nebula Theory (The Nebular Theory) specifically explain?

The Solar Nebula Theory explains that due to gravity a nebula cloud will collapse into a flattened disk and spin. Heat radiate outwards, which allows for cooling and condensing of gases near the center of the disk.

Does an entire body of magma solidify homogenously (at the same rate)?

The entire body of magma does not cool at the same rate

If the primary elements of the universe are hydrogen and helium (occurring in a 3:1 ratio), how do heavier elements (Ca, Fe, Si, O, etc.) occur in any type of concentration

The heavier elements are still apparent in concertation due to stellar nucleosynthesis, which these elements are byproducts of fussion reactions.

The Biosphere

The living part of the Earth (what we belong to). The Biosphere has a great impact on the rest of the spheres due to human influences.

The Mantle

The lower mantle is chemically the same as the upper mantle which is iron rich. It's primarily made of igneous rock, peridoite, but is soft enough to flow. It is also the thickest layer of the five.

Other properties of minerals

The mineral galena feels heavy because it has a high density: because it has lead in its chemical formula, it has an unusually high mass per unit volume Calcite will strongly react with dilute HCl, while dolomite will weakly react Due to high Fe content, magnetite will be strongly magnetic Talc's low hardness and chemical composition gives it a slippery soapy feel This sample of Na-plagioclase feldspar has obvious stripping along the plane of clevage shown. This is called straitations

Deep-Marine Deposits

The ocean basin floor is everywhere covered by sediments of different types and origins. The only exception are the crests of the spreading centers where new ocean floor has not existed long enough to accumulate a sediment cover. Sediment thickness in the ocean's averages about 450 meters (1,500 feet).

The Geosphere

The rocky portion of the planet (surface of the Earth)

Geothermal gradient

The temperaure increases the fauther you drill into the crust, mantel, and core

What is unique about first generation stars?

They are larger, burn hotter, and run out of fuel faster than other stars do

Turbidity Currents

Turbidity currents occur just offshore in a coastal marine environment. The continent extends out beneath the ocean and is covered when sea level rises and is exposed when sea level falls. We refer to this as the continental shelf. Where are the shelf drops off into open water is the true edge of a continent. When covered, sediments from the continent wash over the continental shelf, being deposited along the shelf and beyond. Water currents will carve out paths on the continental shelf and create deep submarine canyons. As water travels through these canyons, it is channelized, causing it to have a higher velocity and energy. It carries quite a bit of sediment as it rushes through and out of the canyon. When it reaches the end of the canyon, all of the sediment is dumped on the sea floor because the water is no longer channelized, and the current loses its velocity and energy. A turbidity current is kind of like an underwater avalanche happening at the end of a submarine canyon.

Agents of Metamorphism Increasing Pressure o Associated metamorphic processes: • P-T Changes Stress • Hydrothermal Fluids

Under extreme pressure, atoms pack more closely togther forming denser minerals - Occurs in all directions equally phase changes/ neocrystallization changing both pressure & temperature Both increase with increasing depth - Example- Below a mountain chain -- 15 km = 450 C, 4.5 kbar -- 30 km = 750 C, 9 kbar Mineral stability depends on both P & T - As depth increases, the orginal mineral assemblage becomes unstable & is replaced with a more stable assemblage Solutions of very hot water chemically react with rock by dissolving & transporting ions

Hot Spots

Unlike island arcs, oceanic hotspots don't have a composition range. They are purely basaltic because they're being fed directly from a mantle plume instead of partial melt rising through the crust. This of course produces shield volcanoes. While Hawaii is certainly an easy place to talk about, is not the only place in the world you can find an oceanic hotspot. Iceland is sitting on top of a hot spot at the top of the Mid-Atlantic Ridge. This is why geothermal energy is so prevalent in that country. However, Hawaii offers a plethora of information about plate movement because there is such a good history preserved in its hotspot track across the Pacific plate. In the case of continental hotspots, the compositions are variable. Some eruptions are purely basaltic, such as what we see with cinder cone eruptions, while others are purely rhyolitic. And of course, all compositions in between occur here too. Interestingly enough, some eruptions are purely pyroclastic, meaning that only pyroclastic debris and tephra is produced. We can observe this range within the hotspot track at Yellowstone.

Addition of Volatiles: Flux Melting

Volatiles are substances that evaporate relatively easily (N2, H2, SO2, H2O, CO2) When volatiles mix with hot, dry rock, they react with minerals present. -Break chemical bonds, causing the rock to melt by lowering the original temperature.

The Discovery of Seafloor Spreading

WWII allowed for more detailed information about the seafloor . Detailed mapping for depth variations (bathymetry). Invention of sonar

Coastal Beach Sands

Waves move sand grains back and forth along the coastline - Well sorted, medium-grained sandstone.

Clastic Sedimentary Rocks

Weathering -> Erosion/ Transport -> Deposition -> Lithification

How does sediment form?

Weathering: combined phenomena that corrode & break up solid rock - Surface process - Discolored/ rough

What problems are associated with accelerated soil erosion?

What problems are associated with accelerated soil erosion?

Observation

What you observe

Bed-Surface Markings

When another turbidity current deposits sediment, another graded bed is deposited on top. So, we get this repeated sequence. Graded beds are not just a product of turbidity currents. We also see this in the terrestrial environment in some riverbeds and alluvial fans. One of the most important things to remember about sediment settling is that coarse grains settle first, followed by progressively finer grains in what is called a fining upward sequence. In this image, A represents a very coarse-grained sandstone, while B represents a fine-grained sandstone. This sequence shows that the coarser sand grains fell out of suspension first followed by the finer sand grains. C is a fine-grained sandstone with preserved ripples in it, indicating it was lying on top of the other sediments and exposed to fluid currents. When the energy was low enough, D was deposited. D is the finest grained sediment and has lithified into shale. Once sediment is deposited, surficial processes and organisms may leave their marks on the bedding surface. For instance, burrowing and or slithering organisms may leave trails and traces of movement through sediment. When fine-grained sediment dries out, it loses water and contracts causing cracking along the surface. We see these mud cracks preserved in the image on the left. We may also see impressions made by rain drops preserved in the same way. If rain falls onto dry sediment and leaves an impression, then is buried by more sediment before the impression is destroyed, the impression is preserved. Additionally, when organisms die, they fall in place and if not moved, will decay in place. All of this activity is recorded and preserved when more sediment is deposited on top of an undisturbed bed. Sediment will bury dead and decaying organisms to create fossils as well as preserve mud cracks and rain drops.

External Processes Example

Wind causes weathering and erosion

Was Wegener right?

Yes, 30 years after his death, his ideas were proven true by technological advances that allowed abservations of the seafloor.

Jointing

a natural crack in rock separates the rock into pieces.

Mineral

a naturally occurring solid, with a definite chemical composition and crystalline structure

bed

a single layer of sediment/rock with a recognizable top & bottom

Hydration

absorption of water into crystal structure of minerals

Shallow-Marine Clastic

areas that are close to shore but always submerged. These areas have a significant amount of mature clastic sediment along with marine algae (like seagrass) as well as skeletal material from animals like coral, echinoderms (sea urchins and sand dollars), and mollusks (clams and snails).

Crystalline Structure:

atoms are arranged in an orderly, fixed pattern

weathering

breakdown of pre-existing rock

Physical Weathering (aka Mechanical Weathering)

breaks intact rock into unconnected grains/ chunks known as clasts. Wentworth scale

Non-Silicate Mineral Groups

carbonates, halides, oxides, sulfides, sulfates, native elements

Clastic (detrital)

cemented-together clasts.

Metamorphic Processes • Recrystallization: • Phase Change: • Metamorphic Reaction/Neocrystallization: • Plastic Deformation:

changes the size and shape of grains WITHOUT changing the chemical make-up Protolith -> Metamorphic Rock transforms one mineral into another with the same composition but different crystalline structure growth of new minerals that are different from the protolith a rock reaches a high enough temperature where it behaves like soft plastic; stress causes grains to change shape

Clast composition

chemical makeup/ mineral composition

Phaneritic

coarse-grained, indicates slow cooling history.

Biochemical

composed of shells

Porphyritic Texture

contains both coarse & fine grains

Intrusive

cooling & crystallization of magma underground (plutonic)

Extrusive

cooling & crystallization of melt materials at the surface (volcanic)

Clast size

diameter of grains

External Processes

driven by energy from the Sun

Internal Processes

driven by heat inside the Earth

Eruption

episode's when volcanoes extrude lava and/ or pyroclastic debris. - Hot magma rises through the crust and emerges at the surface.

Aphanitic

fine-grained Indicated rapid cooling history.

o Metasomatism -

fluids pick up ions of one constituent & leave ions of another, changing the chemical composition of the rock

What are the indicators for determining a depositional environment?

grain size, composition, sorting, structure, and fossils

When planetesimals form, they have a ________________ composition

homogenous

Subhedral:

imperfectly shaped

Nonfoliated:

interlocking, crystalline texture - Minerals grew during mmm - Ideentified by composition

Wedging

joints are opened further by freezing/thawing of water, salt precipitation, and plant roots.

Cross beds

laminations within a bed inclined at an angle.

Phenocrysts

large grains in a fine-grained matrix - Indicates a complicated cooling history -Extrusive

Dunes

like a ripple, but much larger

Foliated:

minerals have a preferred orientation or are concentrated in different layers - Parallel alignment of platy minerals - Alternating light and dark layers - Indenified by composition, grain size, & nature of foliation

regolith

loose debris (sediment and/or soil)

sediment

loose fragments of rocks/ minerals broken off bedrock Crystals precipitate out of water Shells/shell fragments.

Anhedral

lost its shape

Low viscosity magmas

low SiO2 content (mafic composition) = moves quickly

Solid:

maintain its shape indefinitely

cementation

precipitates form a cement that binds grains together.

Chemical

precipitates out of solution

Dynamic Metamorphism

metamorphism occurs due to impact, or a high pressure shock event

Seafloor spreading

new crust moves away from mid-ocean ridges, Old crust must be recycle deep-ocean trenches are places where old crust sinks back down into the mantle

Continental-Continental Convergence - Is subduction involved? - Plate movement: - Geologic features: - Real-world example:

no subduction-> no volcanism, suture zone, mountain belt (crustal thickening), mountains, Him. Mountains

Oxidation

occurs in Fe-bearing minerals; minerals "rusts" to form new minerals

Lithification

occurs when lose clasts become solid rock

Deposition

occurs when sediment settles from its transport medium.

Subduction

oceanic plate will bend & sink beneath an overriding plate

Schistosity

parallel alignment of platy minerals

Euhedral:

perfectly shaped

o Compression: o Tension: o Shear:

push, pull, one side moves sideways relative to the other side

soil erosion

removal of soil by running water or wind Human activities accelerate erosion rates by 10-100 times, so that erosion exceeds formation.

Viscosity

resistance to flow/ how easily a fluid flows Viscosity controls how quickly/slowly magma moves.

Schist: o Grain size: o Protolith: o P-T conditions:

schist may form from any metamorphic rock of a lower grade. That means a schist may form from a phyllite, or slate as well. The rule with metamorphic rocks is that higher grade rocks can form from rocks of another rock type or rocks of a lower grade that have already been metamorphosed. The fine-grained clay minerals in the protolith have been obliterated by this point. Once again, the protolith here is a shale. Higher temps than phyllite conditions-mica crystals are larger

Glacial

sediment of any size can be moved and deposited.

erosion

separating from rock/transport of loose sediment

Differentiation

separation of materials by density

Fractional crystallization

sequential crystal formation as cooling takes place; some chemical components will be removed before others.

strata

several beds together

Crystal

single, continuous piece of a crystalline solid, typically bound by flat surfaces called faces

Ripple marks

small, elongated ridges

compaction

space between grains is removed.

Index minerals

specific minerals that form under certain P- T conditions; their presence indicates MMC grade

Slaty cleavage

splits into thin sheets

stratigraphic sequence/formation

stratigraphic sequence/formation

Slate: o Grain size: o Protolith: o P-T conditions:

the lowest grade foliated metamorphic rock and should look familiar to you. While it exhibits slaty cleavage, which means it splits into thin sheets, it is made up of dark clay sized minerals Clay sized Shale is the protolith of slate Maximum PT conditions slate will give off a metallic clinking noise when tapped with a hammer or other metallic object, while shale will not

Metamorphism

the process in which a pre-existing rock undergoes a solid-state change in response to the modification of its environment

Plate Tectonic Theory

the recognition that the lithosphere is divided into mobile, rigid plates that move over the asthenosphere. Relates seemingly unrelated phenomena, showing how geologic features and events are related.Moving plates= moving continents= Earth's surface is always changing

Scientific Law

theory that works in the same manner anywhere in the universe

basement

usually one of the crystalline rocks, igneous or metamorphic, though it may be a much older sedimentary rock.

Dissolution

water dissolves minerals completely

Hydrolysis

water reacts chemically with minerals to break them down and form new minerals.

Desert

well-sorted sandstones

How are minerals grouped/classified?

~ 4,000 known minerals-how should we classify them? -Product of environment of formation -Certain minerals form in certain environments due to the avaiable elements - Minerals are grouped by chemical compositions (principle negative ion- anion or anionic complex)