Geology 1005 Test 1
Properties of minerals
-Color -Streak -Hardness -Cleavage -Fracture -Luster -Specific gravity -Special Properties
Where is the Cascade Range? Geologically, what is its origin? Why is it considered a volcanic hazard? (Consider its tectonic setting) (pp. 114-115). What about for the Aleutian Islands? What about for the Yellowstone, WY and Long Valley, CA calderas? What is a caldera?
-Western U.S./SW Candada-origin: Pacific NW -string of volcanoes: violent eruptions possible, w mudflow danger, close proximity to major cities -Aluetian: sits above subduction zone so vulnerable to earthquakes and volcanic eruptions; young & active volcanoes and volcanic ash threat -Yellowstone/CA: concerning bc of seismic/thermal activity due to past histories
What effects do volcanic eruptions have on climate?
-been known to erupt toxic gases such as concentrated doses of CO2, carbon monoxide (CO), toxic fluorine gas, sulfur, and hydrochloric acid (HCl) -Large-scale volcanic eruptions can trigger local or global fluctuations in climate, often producing cooling trends and drops in global temperature
How does viscosity affect / influence the extent of lava flow, the type of volcanic eruption, and the shape of the overall volcano?
-low viscosity: quick and easy flow (e.g. water)-high viscosity: slow flow (e.g. honey)- the higher the temperature of magma, the lower the viscosity- the higher the silica content, the higher the viscosity of the magma
What are pyroclastic flows?
-sometimes known as nuée ardente-type of pyroclastic flow where fine ash and hot gases combine to form a type of flaming (or glowing) cloud.-E.g. Mt. St. Helens in Washington, US
What is the difference between a hypothesis and a theory? (p. 8)
1) can take many forms, ranging from a general conceptual framework or model describing the functioning of a natural system, to a very precise mathematical formula relating several kinds of numerical data. 2)is a generally accepted explanation for a set of data or observations.
What is the difference between a conglomerate, a sandstone, and a shale? (pp. 34-36)
1) is coarse to very coarse grained (>2mm) (Rounded clasts) 2) is medium to coarse grained(.06 - 2mm) (mostly quartz) 3) is very fine grained (<.004 mm) (breaks into platy sheets)
What two factors influence how magmas form in the asthenosphere?
1. A reduction in pressure - When material rises from the lower mantle into shallower regions, such as at hot spots or spreading centers, the corresponding reduction in pressure promotes melting of the rock, creating a magma 2. The addition of fluids (such as water) A subducting plate carries a lot of seawater embedded with it. As the plate descends, the water warms up and rises back up into the overlying rocks. The heated water promotes melting of those rocks, creating magma.
What are the three general categorical terms used by geologists to describe a volcano's activity?
1. Active: erupting, or erupted recently, or likely to erupt soon. E.g., Kilauea, a shield volcano in Hawaii. 2. Dormant: has not erupted for hundreds to thousands of years but may erupt again in the future. E.g., Mt. Rainier 3. Extinct: was active in the geologic past but is not likely to erupt again due to changes in the underlying geology. E.g., the volcanoes on the Hawaiian island of Kauai
What is the difference between regional and contact metamorphism?
1. Burial. The deeper a surface rock gets buried underground, the warmer the Earth becomes (about 60°F per every mile of depth, or 30°C / km); and the pressure of the overlying rock will also play a role. Rocks can be buried tens of km underground and then resurface millions of years later as completely different rocks due to metamorphism. Rocks that are metamorphosed this way (deep, large-scale burial) are said to have undergone regional metamorphism. 2. Cooling magma: Similar to how skin will burn if it touches a hot flame, a rock may change its composition if it encounters a hot magma that is rising from deep within the Earth. Rocks that metamorphose this way undergo contact metamorphism. Contact metamorphism occurs when magma (underground lava) rises from the depths of the Earth and resides in a magma chamber of a volcano. The heat from the magma chamber radiates out, altering or metamorphosing the surrounding rocks. The surrounding rock that is closest to the magma chamber - closest to the heat source - undergoes the highest-grade metamorphism (it is altered the most), and the degree of metamorphism lessens further out in a concentric manner.
What are the three kinds of plate boundaries? What is the difference between the three different kinds of plate boundaries? (pp. 50-55)
1. Divergent boundary: two plates move apart from one another (e.g. mid-ocean ridge, continental rift). A type of tensile or extensional stress. 2. Convergent boundary: two plates move toward one another (e.g. subduction zone, continent-continent collision). A type of compressive stress. 3. Transform boundary: two plates slide past one another. A type of shear stress.
What are some of the precursors to a volcanic eruption?
1. Earthquake activity 2. Changes in heat flow 3. Changes in shape 4. Increases in gas and steam emission
What type of lava is found at mid-ocean ridges / makes up the ocean floor? What would be its composition and overall viscosity? What about for felsic lava?
1. Mafic lava 2. Low silica & high mafic mineral content. Low viscosity 3. High silica & low mafic mineral content. High viscosity
What is the difference between mafic & felsic magma?
1. Mafic lava has low silica content and high mafic mineral content (the high magic mineral content gives basalt its black or dark grey color -has low viscosity for a lava and flows relatively easily -the ocean floor is lined in basalt, which has all derived from a mafic lava extruded at mid-ocean ridge -basaltic lavas erupt at temps above 950 C 2. Felsic lava (magma) at the opposite end is a rhyolitic lava (which cools into rhyolite, a felsic igneous rock) A felsic lava has a high silica content and a low mafic mineral content (rhyolite is lighter in color compared to basalt because rhyolite contains few mafic minerals). A felsic lava has a high viscosity and flows slowly: the lava looks "thicker". Recall that continents are underlain by granite, a felsic igneous rock. Felsic lavas are typically cooler temperature lavas, erupting at temperatures as low as 650-750°C (1200-1400°F). Because of their high viscosity, felsic magmas can sometimes plug up the vents of volcanoes, causing the eventual eruption to be much higher in pressure and thus more explosive.
What are the three differentiated layers of the Earth (p. 3, Fig. 1.3 p. 5). What is each layer composed of? What is the difference in composition between the inner core and outer core?
1. Outer crust (oxygen and silicon) 2. Mantle (iron, magnesium, silicon, and oxygen) 3. Core (iron and nickel) a. Outer core - liquid b. Inner core - solid
What are the three different kinds of volcanoes? Where can examples of each type be found? What are some of their defining characteristics?
1. Shield Volcanoes: broad, gentle domes, that when viewed from the side resemble a soldier's shield lying on the ground. Hawaiian Islands 2. Cinder Cones and Pyroclastics: formed from cone-shaped piles of small basaltic rocks (termed lapilli) and blocks: these sometimes form in a single eruption. (Popular sites are in Arizona) 3. Composite Volcanoes: tall, cone-shaped, steep slopes whose slopes aremade of intermixed layers of lava, tephra, and blocky flows. E.g. Mt. Fuji
Name the three major elements/ minerals that affect magmas composition?
1. Silica (SiO2): found in minerals quartz (SiO2) and feldspar (an aluminosilicate mineral) -the silica content of magma ranges from 45%-75% 2. Iron (Fe) 3. Magnesium (Mg) -minerals that are rich in Fe and Mg, like micas (biotite, muscovite), pyroxenes, and amphiboles are called mafic minerals
Which type of lava flow has the lowest viscosity: silica-poor or silica-rich? Which kind has the highest: silicapoor or silica-rich? What two factors influence viscosity?
1. Silica poor 2. Silica rich 3. temperature & silica content
Which areas of the US are at highest risk for major earthquakes? What is an intra-plate earthquake and how does this differ from that along the edge of a plate? (pp. 86-87)
1. Southern Alaska: sits above a subduction zone and a strike-slip fault. 2. California: San Andreas fault runs directly through San Francisco, as well as most of southern and central California (Los Angeles is also affected by off-shoots of this fault) 3. Missouri: the strongest earthquake in the US occurred along the New Madrid fault in Missouri in 1811-1812. Aftershocks continued over the next ten years. 12 million people now live in this area. 4. Charleston, South Carolina: magnitude 6.9-7.3 earthquake took place in 1886 5. Virginia: magnitude 5.8 earthquake in 2011, damaged the Washington Monument and National Cathedral. 6. Pacific Northwest: Portland, Seattle overlie a subduction zone to the west. Note that #3, 4, and 5 are all examples of intra-plate earthquakes: i.e., earthquakes that occur within a lithospheric plate, as opposed to at the border of two tectonic plates. Intra-plate earthquakes are far less common an event, but no less deadly in their impact.
What are convection cells(1) and how does they play a role in plate tectonics? What is the difference between "slab-pull"(2) and "ridge-push"(3)? (pp. 57-58)
1. hot mantle material rises up at spreading centers (MORs), then spreads outward, pulling along the overlying lithosphere with it. Once the mantle material cools, it sinks at subduction zones, pulling the overlying lithosphere with it. The mantle material then rises back up again at the spreading center, creating a circular convection cell (in a typical convection cell, warm fluids rise, cold fluids sink). 2. the weight of the dense, down-going slab of lithosphere in the subduction zone pulls the rest of the trailing plate along with it, further opening up the spreading center at the mid-ocean ridge. Recall that older oceanic lithosphere (> 10 Ma, e.g.) sinks due to its density. As it does so, it pulls the rest of the plate along behind it, like an anchor pulling an anchor line. 3. As new lithosphere is created at mid-ocean ridges, the older material is pushed away from both sides of the midocean ridge axis. MORs have a slope to them, and gravity is thought to play a role in pushing the older basaltic crust further away from the ridge.
What is the difference between a plutonic and volcanic igneous rock with regard to i) their origin and ii) the size of their mineral grains? What is the difference between magma and lava? What is the difference between a basalt and a granite? A granite and a rhyolite? (p. 34)
1. rocks that form from magma, a molten (hot) liquid that exists underground, found either in i) the belly of a volcano -the magma chamber - or ii) intruded underground between other rocks (as dikes and sills, terms to be defined later).are called intrusive, because they form within the Earth, underground. The magma in magma chambers can take thousands of years to cool down and solidify into rock. Because the cooling process is slow, crystals have time to form and can grow large enough to be seen with the naked eye: plutonic rocks are typically coarse-grained. Granite is an example of a plutonic igneous rock: it contains viewable crystals of silicate minerals such as quartz, feldspar, as well as ferromagnesian minerals like mica and amphibole. 2. molten igneous rocks created at or above the Earth's surface, usually extruded from a volcano in the form of lava. Igneous rocks that form above ground are called extrusive. Because volcanic rocks cool quickly, there is less time for large crystals to form, so volcanic rocks are typically fine-grained, most crystals cannot be seen with the naked eye. Basalt, a rock that makes up the ocean floor; and obsidian, a dark, glassy rock, are two examples of volcanic igneous rocks. Magma is lava below ground.
What is a dip-slip fault(1)? What is a hanging wall(2)? What is a foot wall(3)? (pp. 65-66)
1. that triangular-shaped block of rock you see in the figure above, the part that lies above the fault surface (in either figure above) is called (2), the triangular block below the fault surface is called the (3).
What is the difference between the (1)focus and the (2)epicenter of an earthquake? (p. 64)
1. the point on the fault, within the Earth (i.e., underground), from which the earthquake energy propagates. The source of the quake. Also called the hypocenter. 2. the point on the Earth's surface directly above the focus (this can be marked on a surface map).
Mineral
A solid inorganic substance of natural occurrence.
Electrons
A subatomic particle with an electrical charge of -1; generally found orbiting an atomic nucleus
What are hot spots? How do they form? How do they provide evidence for plate tectonics? Where can examples be found, both within the continental US and within the oceans? (pp. 56-57)
As discussed previously in class, not all volcanoes are found along plate boundaries. E.g., the volcanic island of Hawaii lies in the middle of the Pacific Plate, while the volcano that underlies Yellowstone National Park, Wyoming, lies within the North American plate. These are examples of hot spot volcanism. These volcanoes are thought to form above a localized magma source (called plumes) that rise up from deep within the Earth, and whose position in the mantle has remained fixed relative to the moving plate above it. As the crust slowly moves over the fixed mantle plume, the original volcano loses its magma source and eventually goes extinct: the new patch of crust that lies over the mantle plume spouts a newer, younger volcano. Eventually, the younger volcano moves past the hot spot, goes extinct, and a third volcano arises. Over time, this process forms a series or chain of volcanoes, creating a hot spot track that records the motion of the lithospheric plate, as seen in the Hawaiian islands and the Hawaiian-Emperor seamount chain (p. 57, Fig. 3.22), where the youngest volcano is closest to the hot spot.
Why is the age of the seafloor no older than 200 million years old, whereas continental crust has been discovered that is over 4 billion years in age? (pp. 46-47)
As seafloor spreading progresses, previously formed rocks are continually spread apart and moved further from the ridge, while fresh magma rises to form new sea floor at the ridge
What were five different lines of evidence Wegener provided to show that the continents moved?
Coastlines. Glacial activity Fossil evidence: plants Fossil evidence: animals. Rock assemblages.
Was Wegener's idea of continental drift accepted by the geologic community? Why or why not? (p. 43)
Despite all this evidence, Wegener lacked a mechanism to explain how the continents actually moved. It was this lack of a mechanism that caused his idea to be discredited, until its revival in the 1960s, when Wegener's theory of continental drift became incorporated as part of a larger theory called plate tectonics: the large-scale movement and deformation of the earth's outer layers.
What is a mid-ocean ridge (seafloor ridge)? (p. 45)
Divergent boundaries in the ocean
What are the four most common chemical elements in the Earth? What are the four most common elements in the Earth's crust? (Table 1.2, p. 5)
Earth - iron, oxygen, silicon, magnesium Crust - oxygen, silicon, aluminum, iron
Cleavage
For many minerals, when they are broken into smaller pieces, the manner in which they break is not random. When a mineral breaks to form smooth flat surfaces that have a specific orientation in relation to the overall crystal structure, those planar surfaces are called cleavage planes. You will see examples in lab. Minerals may have 1, 2, or 3 sets of cleavage planes depending on the strength of the bonds holding the atoms together. Mica, which breaks off in thin sheets, has one plane of cleavage. So does graphite (discussed above). Halite (salt), which resembles small cubes when it breaks apart, has three cleavage planes.
What is the concept behind paleomagnetism? What is a magnetic reversal? What is the Curie temperature? (pp. 43-44)
Geologists realized that once a rock cools down, the magnetic minerals remain fixed and do not realign / reorient themselves if the rock formation drifts elsewhere over time. The rock thus maintains a historical marker of the Earth's past magnetic field - the study of which is called ______ (fossil magnetism) - which geologists use to determine the approximate location (latitude) where the rock originally formed. As igneous rocks cool from a molten magma, the rocks cool below a specific temperature called the _______ (named after Pierre Curie, who discovered this property in 1895; the temperature of the _______ varies depending on the rock: for magnetite, the ______ is 585°C [1085°F]. The melting temperature of magnetite is 1538°C or 2800°F). Above the____ point, a rock loses any magnetism it contains, below the _____ point, the rock's many iron crystals align with the current orientation of the Earth's magnetic field (like how a compass needle aligns north).
What are some of the major hazards related to earthquakes? (e.g. aftershocks, tsunamis, etc.) (pp. 70-80) What is liquefaction and what hazard does it play when designing buildings to withstand earthquakes? (pp. 75-76)
Ground motion, aftershocks, ground failure, tsunamis, fire Earthquake vibrations can cause beds of wet sand or silt to lose their cohesion (the soil particles separate from one another) and become a slurry, like quicksand, unable to support whatever it on top of it (e.g., a building). The soil undergoes liquefaction as a result of the intense shaking, and the buildings tip over.
What is a strain?
If the object is deformed as a result of that stress, causing a change in the object's shape, the resulting deformation is called strain.
Where are earthquakes more likely to occur: in the lithosphere or the asthenosphere? Why? (p. 66)
Lithosphere at plate boundaries - movement
What is a transform plate boundary, what type of plate motion is involved, and what type of geological features result from them? Where can examples of these be found? (p. 55)
Mid-ocean ridges are not long, continuous, uninterrupted undersea volcanic mountain chains, but rather short segments that are appear to be offset by fracture zones. It was originally thought that the entire length of the fracture zone - which can extend miles beyond the width of the mid-ocean ridge, was made by a type of fault called a transform fault, but it was later discovered that only the area of the fracture zone within the mid-ocean ridge itself showed any earthquake activity (and hence, movement). The area where the active movement of the fracture zone occurs is called a transform fault: in a transform fault, two plates slide past one another in opposite directions (one plate moves left, the other right), in a shearing motion. As a result of this shearing motion, earthquakes - commonly associated with transform faults - can occur.
What is a continental fissure eruption and where is a classic locality in the US?
Most volcanic rock is created along the 50,000 km (30,000 mi) of spreading centers called mid-ocean ridges along the ocean floor. It is here that magma rises up through cracks in the lithosphere, a type of eruption called a fissure eruption.-Columbia Plateau: spread out over western Washington and Oregon, and eastern Idaho
Fracture
Not all minerals break smoothly along cleavage planes. Minerals that have no cleavage at all break to form irregular surfaces called fractures, or they may form a smoothly curving, clamshell-shaped surface called a conchoidal fracture. The minerals quartz and obsidian both display conchoidal fracture, as does glass. In fact, Stone Age tools such as flint (a variety of quartz) were made using minerals that expressed this property: the conchoidal fracture gave the rock a razor-sharp edge for hunting and slicing meat.
Coastlines
On appearance alone, many continents look like they could fit back together: e.g., South America and Africa.
If the entirety of Earth's history were laid out in a 24-hour day, when does our species, Homo sapiens, arrive? (p. 7).
Our species arrived in the last 10 seconds before the year itself ends, or December 31, 23:59:50
What did Wegener name his supercontinent? What happened to it? (see also lecture notes, Ch. 3, p. 1)
Pangea. It split.
How are earthquakes and their associated ground movement recorded? How is the epicenter of an earthquake determined? (pp. 68-69)
Seismometers measure and record ground movement in vertical and horizontal directions To determine where the exact epicenter is on a map (direction), S-P arrival times from at least three different seismic stations are recorded, a method called triangulation (see p. 69, Fig. 4.9).
What is the difference between elastic, plastic, and brittle deformation? .
Softer materials that can change their shape without breaking (e.g. stretching a rubber band, bouncing a rubber ball) undergo elastic deformation. These materials deform because the bonds that hold the atoms of that substance together rupture but then quickly reform, allowing the material to stay whole. In addition, the material returns to its original shape after the stress is gone. There is an upper limit to how far something can be deformed elastically but still not break: this is called the elastic limit. Plastic deformation: beyond the elastic limit, the object can be deformed (undergoes strain) but does not return to its original shape. The changes are permanent (e.g. a glass blower folding hot glass; a rock layer undergoing folding). Materials that undergo brittle deformation break without taking on any change in shape (strain): e.g., a glass or plate that falls and shatters on the floor. The break occurs because the bonds that hold the atoms of that substance together rupture. Brittle deformation is characteristic of rocks are low temperatures and pressures near the Earth's surface, leading to fractures and faults (described in Ch. 4).
In general, most of the world's volcanoes are associated with what kind of tectonic activity?
Subduction zones and the remaining are associated with hot spots or continental rift zones
What are pyroclastics?
The general term used to describe the rocky debris (as opposed to lava) that erupts out of a volcano
What is the seafloor spreading hypothesis? Who proposed the idea? How does the discovery of magnetic stripes on the ocean floor tie in with support for plate tectonics? (pp. 45-46)
The hypothesis proposed that new seafloor (new oceanic crust) was created at the mid-ocean ridges which then pushed the older crust away from the mid-ocean ridge on either side. The new seafloor produced at the mid-ocean ridge rose in the form of magma from deep within the Earth's mantle. Upon reaching the surface, the magma quickly cooled into rock, passing the Curie point as it did so, and so acquired the Earth's present magnetic field polarity (normal or reversed). As more magma rose up, the older materials were pushed apart on either side, and very, very gradually, on an pace of a few mm / year, the ocean floor slowly widened with time.
What is a lithospheric plate? What is a plate boundary?
The lithosphere is broken up into ~20 lithospheric plates. The contacts between the plates are called plate boundaries: of which 12 are major plates (large in size) and the rest are microplates (smaller in size). Some plates consist entirely of oceanic lithosphere, some have both continental and oceanic lithosphere. Plate boundaries are identified by the location of earthquakes, which occur in relatively narrow, distinct belts called seismic belts.
What is the difference between basalt & rhyolite?
The main difference between basalt and rhyolite is that basalt usually appears in dark colours, while rhyolite usually appears in light colours. Both rhyolite and basalt are types of extrusive igneous rocks
Rock Assemblages
Wegener found similar assemblages of rock formations across different continents: e.g., he noticed that a band of Precambrian rocks (from 540 Ma) on the east coast of South America matched those of a similar assemblage off the west coast of Africa, two continents currently separated by an ocean. If the continents had once been together, these matching rock groups would have been adjacent to one another and formed a continuous band of rock. Wegener proposed that not only did the coastlines of these continents match, but also their fossil and rock assemblages. An example cited by your textbook notes that the Appalachian Mountains of eastern North America continues as the Caledonian range of Greenland and the British Isles: all three land masses were a single unit at one point in time (the mountain chain was long, continuous mountain belt) until the continents drifted apart ("Caledonia" = Latin name for Scotland).
Fossil evidence: plants
Wegener mapped the occurrences of three species of fossil plant (the most widely cited is the genus Glossopteris, an extinct fern) from the late Mesozoic (~100 Ma) and found that these fossils appeared over several - currently unconnected - southern continents. Wegener argued that the only way this could occur was if the continents were once all joined together: otherwise how could the plants have migrated across the sea?
Fossil evidence: animals
Wegener mapped the occurrences of various fossil animals, including a small, extinct, aquatic reptile called Mesosaurus, and found a distribution similar to that of the plants
Glacial activity
Wegener, who was a meteorologist, observed i) glacial striations (scratch marks left on rocks by glaciers) and ii) till deposits (till = rocks carried by the glacier and left behind after the glacier melted) in sediments in southern South America, southern India, and southern Australia that dated back to the late Paleozoic (300 million years ago): even though South America, Australia and India currently reside nowhere near the south pole. He noticed that the striations ran from the sea toward the continents: the opposite way in which modern glaciers move (glaciers form on land and flow to the sea). Wegener plotted the orientation of the striations and realized that i) the pattern would only make sense if the above continents were once all joined together (thus forming a single continental ice sheet), and that ii) part of Pangaea had to be at polar latitudes for the glacial ice sheet to develop in the first place.
What is the difference between geographic north and magnetic north? What specific layer within the Earth generates the Earth's magnetic field? What is magnetic declination?
When a compass needle points north-south, it does not point to the geographic north and south poles! Rather ,it points to the magnetic poles, which are (currently) roughly 10° off from the geographic pole. So, geologists define two "norths" and two "souths": geographic north versus magnetic north, and geographic south versus magnetic south. The magnetic poles are created by the Earth's magnetic field. The Earth's magnetic field is generated in the Earth's outer core The difference in angle between the geographic north pole and the magnetic north pole is called the magnetic declination. Declination varies depending on what latitude and longitude you live at. The current declination for our region is about 10°.
What is a subduction zone? What happens to the sinking plate? How is it determined which plate sinks?
When two plates collide, the denser plate bends and slides under down the overriding plate, forming a _______ Keep in mind the following: 1. Oceanic crust is composed of basalt, continental crust is composed of granite 2. Basalt is a denser rock than granite (basalt is composed of denser elements than granite) 3. Thus, oceanic crust is denser than continental crust.
Who was Alfred Wegener and what was continental drift? (pp.41-43)
a German geophysicist and meteorologist. In 1915, he published a book entitled "The Origin of the Continents and Oceans." The book hypothesized that the Earth's continents moved gradually over time and that, millions of years ago, the continents once fit together into a large supercontinent which was Pangaea. his theory was continental drift
Hardness
a mineral's ability to resist scratching. We use a metric called the Mohs Hardness Scale to help identify minerals (see p. 27, Table 2.1). The scale lists the relative hardness of 10 standard minerals, with talc (a soft mineral) at #1 and diamond (a hard mineral) at #10. On this scale, your fingernail has a hardness of 2.5, glass has a hardness of 5.5, and quartz has a hardness of 7.
What is a rock? (p. 32) What are the general three categories of rock? Be familiar with the rock cycle (p. 33) and how the three rock types - igneous, sedimentary, and metamorphic - are linked. (p. 39)
a naturally occurring solid that is made up of one or more minerals, or mineral materials (e.g., glass, which forms from volcanoes). Three categories: 1. Igneous rocks: form by crystallizing (cooling) from molten material (e.g., magma in a volcano) at very high temperatures. 2. Sedimentary rocks: form from sediment, or from the breakdown of pre-existing igneous or metamorphic rocks 3. Metamorphic rocks: form from the transformation of pre-existing igneous, sedimentary, or metamorphic rocks
How is the magnitude of an earthquake determined and (in general) what is the difference between the Richter scale(1) and the Mercalli intensity scale(2)? What is the difference between magnitude, amplitude, and intensity, in reference to earthquakes? What is the difference between an earthquake of magnitude 4 vs one of, say, magnitude 3 with regard to ground movement? ...with regard to energy released? (pp. 68-71)
a quantitative (objective) scale [quantitative refers to a numerical term, e.g. "It's 32.0°F outside," or "This dinosaur humerus is 2.2 m long."]. E.g. 1 The amount of ground motion is related to the magnitude of the earthquake. The current system, called the ___, was first developed by American seismologist Charles Richter in 1935 (and since modified), and based on the amplitude recorded by the seismometer at seismic station ideally 100 km from the epicenter. Amplitude refers to amount of back-and-forth or up-and-down motion of the ground. The larger the motion, the higher the amplitude recorded by the seismometer pen. The Richter scale typically goes from 1.0 (mild) to 10.0 (severe). (1) is logarithmic: each increase in number represents a 10-fold increase in the maximum ground motion, and a ~30-fold increase in energy. A magnitude 8 quake is 10x stronger than a magnitude 7 quake, and 1,000x greater than a magnitude 5 quake. A magnitude 8 quake releases 30x more energy than a magnitude 7 quake, and ~1 million times more energy than a magnitude 4 quake. There are about 100,000 magnitude 3 quakes each year, but only 1-2 magnitude 8 quakes annually. Intensity: a qualitative (subjective) scale [qualitative refers a descriptive term, e.g. "It's cold outside."]. E.g. 2 2 is based on the impact of the earthquake
What is a porphyry? What does it imply about how the rock cooled? (pp. 34, Fig. 2.11 D p. 35)
a rock that begins as a plutonic igneous rock but is erupted out of the volcano before completely cooling, and instead finishes its cooling quickly as a volcanic rock
What is the difference between the following fault types? Be able to either draw or recognize the difference between the fault types listed below. (pp. 65-66; see also Lecture Handout, pp.1-2)
a. normal fault - the hanging wall slides down relative to the foot wall. This type of fault motion is observed during an extensional tectonic event, such as continental rifting and mid-ocean ocean rifts. b. reverse fault - the hanging-wall slides up relative to the foot wall. This type of fault motion is characteristic of tectonic compression of the crust (convergent plate boundaries), as happens when two tectonic plates collide. c. thrust fault - Thrust fault: a special type of reverse fault where the fault angle slope is 30° or less. A thrust fault is also called a low-angle reverse fault. d. Strike-slip faults: the plates slide past one another along the fault horizontally; there is no up-or-down motion, and no deformation may be involved. There are two types of strike-slip faults: 1) Right lateral strike-slip fault: if you are facing the fault and looking across at the other side, if the block across the fault slipped to your right, it is a right lateral strike-slip fault. 2) Left lateral strike-slip fault: if you are facing the fault and looking across at the other side, if the block across the fault slipped to your left, it is a left lateral strike-slip fault. e. oblique fault - combo of dip slip and strike slip faults. Occurs on diagonal plane
Inorganic
almost all minerals are not organic chemicals, with some exceptions, e.g., bat guano (apparently crystals grow in ancient deposits of bat guano). Technically speaking, coal is also not a mineral, since it is largely composed of organic matter. Also, minerals are crystalline, and keep their shape indefinitely, due to their crystalline atomic structure (see #4, below). This is as opposed to glass and plastic, which, while solid, are not crystalline. The arrangement of atoms in glass and plastic is disordered.
Neutrons
an electrically neutral subatomic particle with a mass approximately equal to one atomic mass unit; generally found within an atomic nucleus
anions
an ion with a net negative charge
Cations
an ion with a net positive charge
What is a fault? What is an earthquake? (p. 64)
are fractures (breaks) in beds of rock where sliding (movement) has occurred. That energy is released when the stress exceeds the rupture strength of the rock, resulting in sudden movement, or an _____ (also called a seismic slip event).
Naturally occurring
as opposed to being formed synthetically, or manufactured
What are lahars?
ash flows that combine with water that turn into fast-moving debris flows
Ions
atom that has gained or lost electrons, so it has a net electrical charge
Isotopes
atoms of a given chemical element having the same atomic number but different atomic mass numbers
ionic bonds
bonding due attraction between oppositely charged ions. Table salt, whose chemical formula is NaCl (read as "sodium chloride"), is an example of an ionic bond, where Na+ is the cation, and Cl- is the anion. The mineral version of salt is called halite.
covalent bonds
bonding involving sharing of electrons between atoms Water (formula: H2O) and hydrochloric acid (formula: HCl)
Color
certain minerals have a consistent color (e.g. the mineral malachite is green, the mineral azurite is blue, and gold is, well, gold); while others display a spectrum to due impurities that may be in the crystal structure (e.g. pure quartz is glassy, but a variety called rose quartz is pink, and amethyst is a quartz tinted purple). The mineral corundum is colorless in its pure form, but various impurities can turn it into gems such as rubies and sapphires.
What are feldspars? (p. 29)
composed of silicon, oxygen, aluminum, et al., are the most abundant silicate mineral in the Earth's crust (the thin outer layer of the Earth).
P-waves (P stands for primary)
compressional body waves. These are the fastest waves and can pass through both solid and liquid media. As they pass through the Earth, the material is alternately compressed and expanded.
What are carbonate rocks? Provide an example. Where are they typically found / formed? (pp. 29-30; see also Table 2.2, p. 31, for summary of non-silicate mineral groups)
contain 1 atom of carbon bound to 3 atoms of oxygen (written as CO3). The most common carbonate mineral is calcite (CaCO3, also called calcium carbonate), which forms the rock limestone. Limestone forms by precipitating out of seawater, and is the major component of coral reefs (calcite also forms the mineral component your own skeleton).
What are ferromagnesian minerals? What are some common (well, common to geologists) examples? (p. 29)
contain some amount of iron and/or magnesium, two other common elements found in the Earth's crust. These minerals are collectively termed and are usually darker in color (black, brown, green). Olivine (#1 in the silicate list above), for example, is called "olivine" because it is green in color: its formula is (Mg, Fe)2SiO4, and it is abundant in the Earth's mantle (the middle layer of the Earth).
Definable chemical composition
contains a chemical formula, of one or more elements. Examples of minerals containing just one element are the minerals diamond and graphite - each consists solely of the element carbon. Some minerals contain over ten elements.
Abyssal plains
deep, wide, flat regions of the ocean floor that lay 4-5 km below sea level.
What is stress? What are the three main types?
defined as a force acting on an object per unit area (the amount of force acting on a specific area of an object). 1. Compressive stress: when a rock is squeezed (like the walls of the trash compactor closing in on Luke, Leia, Han, and Chewbacca in Star Wars, Episode IV: A New Hope (1977), the rock shortens (or flattens) as a result. Geologically, this occurs when two tectonic plates collide (see below). 2. Tensile stress (extension): when a rock is stretched or pulled apart, tension is produced. Geologically, this occurs at mid-ocean ridges (which are a type of spreading center) as oceanic crust is pulled apart. 3. Shear stress: one part of a rock moves sideways past another across a plane, similar to how a deck of cards slide past one another when shuffled. Geologically, this occurs with transform (strike-slip) faults (see below).
What is a flood basalt?
large volumes of magma that come welling up from the asthenosphere when zones of weakness in the lithosphere provide suitable openings-E.g. India & Brazil
What is the difference between intrusive and extrusive igneous rock?
lava cools to form extrusive igneous -the lava has been ejected from a volcano and cools on the Earth's surface magma cools to form intrusive igneous rocks -the magma cools inside the volcano, forming an intrusive rock that remains inside the Earth
What are sheet silicates (micas)? (p. 29)
layer silicates or Phyllosilicates Each tetrahedron shares three oxygen atoms with its neighbors. Other ions can fit between the sheets. Examples include minerals such as micas and clays.
Solid
means that the mineral maintains its shape, and unlike liquids and gases, does not conform to the shape of its container (glacial ice is technically a mineral, but liquid water is not).
What are native elements? Provide an example. (p. 31)
mineral consists of a single element. The metal atoms are bonded by metallic bonds. E.g., copper (Cu), gold (Au), silver (Ag), tin (Sn), iron (Fe), platinum (Pt), etc.
What are silicates? What is the general chemical formula of a silicate mineral? What is the best-known silicate and what is its formula? (p. 28-29)
minerals containing silica General chemical formula: SiO2 The best known is quartz, whose chemical formula is SiO2.
Luster
minerals that have a metal shine to them are called metallic, those that do not are called nonmetallic (aka glassy, earthy, silky).
What is a convergent plate boundary, how many different types are there and how are they distinguished? Where can examples of each be found? What landforms do they produce? (pp. 52-54)
occur when two plates collide with one another. There are three kinds, depending on the type of lithosphere that makes up each plate: 1. Ocean-ocean: a plate of oceanic lithosphere collides with another plate of oceanic lithosphere 2. Ocean-continent: a plate of oceanic lithosphere collides with a plate of continental lithosphere 3. Continent-continent: a plate of continental lithosphere collides with another plate of continental lithosphere
What is the definition of a metamorphic rock?
one that forms when a pre-existing rock (called a protolith) undergoes a solid-state (does not melt) change in response to being buried and subjected to high temperatures, pressures, and/or reacts with hydrothermal fluids. The process is called metamorphism. The temperatures are typically high, but not high enough to cause the rock to completely melt. Because the rock remains in a solid state, what happens during metamorphism is that the rock recrystallizes internally: the atomic crystal lattice that makes up the rock reconfigures itself into a different - usually stronger - shape.
Formed by geologic processes
produced in one of two methods a. solidification of molten rock (e.g. magma basalt), or direct precipitation from a water solution (e.g., halite); b. precipitated by organisms (e.g. limestone can form from the animal coral): aka biogenic minerals
How do sedimentary rocks form? What are the two general categories of sedimentary rock? Within each category, how are the rocks organized / classified? What is lithification? (p. 34)
rocks that form at or near the surface of the Earth in one of several ways: 1. by the cementing together of loose clasts (fragments or grains) that had been produced by physical or chemical weathering of pre-existing rock 2. by the growth of shell or by the cementing together of shells and shell fragments 3. by the accumulation and alteration of organic matter derived from living organisms 4. by the precipitation of minerals directly from surface-water solutions. 1. Clastic: consist of cemented together clasts (clasts = grains, fragments of other rock that have broken off of pre-existing rock through either physical or chemical weathering) In general, clastics are classified by the average grain size that makes up the rock. 2. Chemical: form from precipitated crystals or grow from solution. b) the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock.
S-waves (S stands for secondary)
shear body waves. These waves arrive second and cannot pass through liquids. the material is moved side-to-side.
Special properties
some minerals have properties that are unique and distinctive: e.g., calcite (CaCO3) effervesces (it forms bubbles) in hydrochloric acid (HCl); halite (NaCl) tastes salty; the mineral magnetite is magnetic, etc.
Roughly, how fast do plates move? (p. 57)
speed ~1 cm/year to ~10 cm/year. The speed is different from plate to plate, and can depend on how much active the plate currently is.
Protons
subatomic particle with a charge of +1 and a mass of approximately one atomic mass unit; generally found within an atomic nucleus
L waves (L stands for Love, named after a seismologist)
surface waves that cause the ground to ripple side-toside like a snake
R waves (R stands for Raleigh, a physicist)
surface waves that cause the ground to ripple up and down.
What is carrying capacity? What happens to the growth of a population as it reaches its carrying capacity? Is carrying capacity a fixed number? Why or why not? (p. 15. also see lecture notes, p. 5)
the ability to sustain population at a basic, healthy, moderately comfortable standard of living. The growth rate should slow down as it is reached. not a fixed number - math equation thing
Crystalline structure
the atoms in a mineral are arranged in a specific, repeating, orderly pattern (similar to a wallpaper or textile pattern, but in 3-dimensions): this is also known as a crystalline solid. The pattern that the framework of atoms composes is called a crystal lattice. (Other texts also include #6, below, in their definition)
Nucleus
the center of an atom, containing protons and neutrons
Streak
the color of a powder produced by pulverizing the mineral, usually obtained by scraping the mineral against a ceramic plate. The color of a mineral's streak of a mineral is not always the same as the color of the mineral itself. E.g., pyrite (fool's gold) appears gold, but its streak is black.
atomic number
the number of protons in an atomic nucleus; characteristic of a particular element
What is the lithosphere? Is it the same thing as continental crust? What is the difference between oceanic and continental lithosphere? (p. 50)
the outer "shell" of the Earth, 100-150 km thick), this layer is "rigid," it does not flow: it is brittle, its materials bend or break. The thickness of the lithosphere varies: a. is thin under the oceans, where it reaches a depth of 50 km (30 mi). b. is thicker under the continents, where it reaches a depth of 250 km (150 mi). Note: ____ and crust are not synonyms: the ______ incorporates i) all of the crust and ii) part of the upper mantle.
What is the asthenosphere? How does it differ from the lithosphere? (p. 50)
the portion of the mantle that flows, this layer is "plastic". It lies directly under the lithosphere, and extends to a depth of 300 km (200 mi) into the mantle. While it is mostly solid, as it is part of the mantle, its high temperatures and pressures allow the rocks within it to flow plastically under stress: grains of rock within it have "partially melted".
Specific gravity
the ratio of a mineral's density (mass/volume) relative to the density of water. Water is 1.0.
Atom
the smallest particle into which a chemical element can be subdivided
atomic mass number
the sum of the number of protons and the number of neutrons in an atomic nucleus
Deep-ocean trenches
troughs that descended to depths > 8-10 km underwater were found along much of the perimeter of the Pacific Ocean (the deepest part of that trench, the Mariana Trench in the western Pacific Ocean near Guam, was found to be nearly 11 km deep. By comparison, the world's highest peak, Mt. Everest, is only 9 km high). All undersea trenches appeared to run along the border of land-based regions known for their volcanism. Now called volcanic arcs, these are chains of active volcanoes: some arcs form a chain of islands (such as the Aleutian islands, off the Alaska Coast), while other arcs fringe the edge of continents (the Andes mountains of South America).
What is a divergent plate boundary, what does it form, and what happens at this boundary? Where is such a boundary found? (p. 52)
two lithospheric plates move apart. Mafic magma rises up from the mantle to fill in the space, often erupting out through volcanoes that form in divergent boundaries (earthquakes are also common here). As the magma cools, it forms new crust (the new crust can be either oceanic or continental, depending on where the spreading center has formed).
Mid-ocean ridges (MORs)
undersea volcanic mountain ranges that stretched for several thousand km, and whose peaks rose 2-2.5 km below sea level. A notable one ran north-south in the Atlantic Ocean, halfway between the Americas and Europe/Africa. MORs were noted for being roughly symmetrical: the profile on one side of the ridge was roughly a mirror image of the other. Perhaps most notable about MORs was that they all turned out to be linked: they were quickly realized to be a global system and active both volcanically and seismically (i.e. produced earthquakes).
In reference to population growth, what is exponential growth? What does an exponential growth curve look like? What is doubling time? (pp. 13-14)
when the population growth rate is constant, and the individuals added per unit of time increases over time. looks like a J 2) is the length of time required for a population to double in size.