EES 101 Exam 3 Study Guide AKA my hell on earth
When did the last glacial period end?
12,000 years ago
Syncline
A downward fold in rock formed by compression in Earth's crust
plunging fold
A fold in which the hinge line (or axis) is not horizontal.
Unconformity
A place where an old, eroded rock surface is in contact with a newer rock layer.
geologic time scale
A record of the geologic events and life forms in Earth's history.
Types of Strain in geology
A rock's response to stress depends on the rock type, the surrounding temperature, and pressure conditions the rock is under, the length of time the rock is under stress, and the type of stress. Rocks have three possible responses to increasing stress (illustrated in figure 3): elastic deformation: the rock returns to its original shape when the stress is removed. plastic deformation: the rock does not return to its original shape when the stress is removed. fracture: the rock breaks.
radioactive decay
A spontaneous process in which unstable nuclei lose energy by emitting radiation
Pangea
A supercontinent containing all of Earth's land that existed about 225 million years ago.
Factors controlling rock strength and deformation type.
At the Earth's surface, rocks usually break quite quickly, but deeper in the crust, where temperatures and pressures are higher, rocks are more likely to deform plastically. Sudden stress, such as a hit with a hammer, is more likely to make a rock break. Stress applied over time often leads to plastic deformation.
Isotope
Atoms of the same element that have different numbers of neutrons
main criticism of Continental Drift
Because he could not explain a mechanism that would cause the Earths' crustal plates to shift around, his idea was dismissed at the time. He also had rates of movements for his continents that seemed very unlikely - too high. It took another 50 or more years for the current plate tectonic theory to become accepted by geologists. This was the result of more evidence being found, including the idea of mantle convection plumes that drive plate movement. Lack of a mechanism for continents to plough through oceanic crust
If given the half life of a radioactive isotope and the % remaining after decay, be able to give an age for that object
Carbon-14 has a half life of 5730 years, meaning that 5730 years after an organism dies, half of its carbon-14 atoms have decayed to nitrogen atoms. Similarly, 11460 years after an organism dies, only one quarter of its original carbon-14 atoms are still around. Because of the short length of the carbon-14 half-life, carbon dating is only accurate for items that are thousands to tens of thousands of years old. Most rocks of interest are much older than this. Geologists must therefore use elements with longer half-lives. For instance, potassium-40 decaying to argon has a half-life of 1.26 billion years and beryllium-10 decaying to boron has a half-life of 1.52 million years. Geologists measure the abundance of these radioisotopes instead to date rocks.
Current geologic era
Cenozoic Era
How is Plate Tectonics theory different from Continental Drift?
Continental drift was rejected at the time it was proposed despite substantial evidence to support the theory. The rejection was based on several factors. Continental drift challenged the prevailing theories of uniform processes, and the geosyncline theory of mountain building. The evidence for Continental drift indicated that the Continents had separated at timeline that went against the proposed evolutionary timeline for the fossil record. Most telling there was no proposed mechanism for what force could move the massive continents. Plate tectonics was developed after World War II. Studies of the Atlantic Sea floor due to submarine warfare revealed the existence of the midAtlantic ridge and seafloor spreading. The magnetic zones were symmetrical on both sides of the Mid Atlantic ridge indicating that the lava coming up from the ridge was creating new ocean floor and pushing the crust apart. This evidence lead to the theory of convection currents that provided a mechanism for the movement of the massive continents. Studies of the spreading of the rift valley and discovery of subduction zones that absorb the extra crust created by the mid ocean ridges solidified the theory of plate tectonics. Still some evolutionary scientists such as Gaylord Simpson resisted the theory up through the 1970's because of the disagreements between their theories of Darwinian evolution and the timeline of plate tectonics. Adjustments were made to both theories and plate tectonics is now a widely accepted scientific theory.
Know the following Plate boundaries in terms of what happens, what features are formed, and examples discussed in class: Transform, Divergent , Convergent (Oceanic-oceanic, Oceanic-continental, Continental-continental)
Convergent boundaries: where two plates are colliding. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. The denser plate is subducted underneath the less dense plate. The plate being forced under is eventually melted and destroyed. i. Where oceanic crust meets ocean crust Island arcs and oceanic trenches occur when both of the plates are made of oceanic crust. Zones of active seafloor spreading can also occur behind the island arc, known as back-arc basins. These are often associated with submarine volcanoes. ii. Where oceanic crust meets continental crust The denser oceanic plate is subducted, often forming a mountain range on the continent. The Andes is an example of this type of collision. iii. Where continental crust meets continental crust Both continental crusts are too light to subduct so a continent-continent collision occurs, creating especially large mountain ranges. The most spectacular example of this is the Himalayas. 2. Divergent boundaries - where two plates are moving apart. The space created can also fill with new crustal material sourced from molten magma that forms below. Divergent boundaries can form within continents but will eventually open up and become ocean basins. i. On land Divergent boundaries within continents initially produce rifts, which produce rift valleys. ii. Under the sea The most active divergent plate boundaries are between oceanic plates and are often called mid-oceanic ridges. 3. Transform boundaries - where plates slide passed each other. The relative motion of the plates is horizontal. They can occur underwater or on land, and crust is neither destroyed nor created. Because of friction, the plates cannot simply glide past each other. Rather, stress builds up in both plates and when it exceeds the threshold of the rocks, the energy is released - causing earthquakes.
radiometric dating
Dating using decay of radioactive isotopes.
Wegner's evidence for Continental Drift (We learned 5 of them)
Distributions of fossil plants and animals, distributions of modern plants and animals, geographic fit of the continents and features, paleoclimatic oddities such as glacial till, coral reefs, and coal. 1- Geological "fit" evidence is the matching of large-scale geological features on different continents. It has been noted that the coastlines of South America and West Africa seem to match up, however more particularly the terrains of separate continents conform as well. Examples include: the Appalachian Mountains of eastern North America linked with the Scottish Highlands, the familiar rock strata of the Karroo system of South Africa matched correctly with the Santa Catarina system in Brazil, and the Brazil and Ghana mountain ranges agreeing over the Atlantic Ocean. 2-fossil relevance. There are various examples of fossils found on separate continents and in no other regions. This indicates that these continents had to be once joined together because the extensive oceans between these land masses act as a type of barrier for fossil transfer. Four fossil examples include: the Mesosaurus, Cynognathus, Lystrosaurus, and Glossopteris. One explanation is the species could have migrated via a land bridge or swam to the other continents. 3-4-Glacial Scratch Evidence/ Mountain Range Evidence- dragging rocks across places, large scratches in places that no longer have glaciers. Scratches in places that line up on other continents, as if they were once connected. It is the same idea for the mountain range evidence, only that the mountain ranges fit together like puzzle pieces. 5-Magnetic Pole Idea- Earth's magnetic field is like a bar magnet with the ends of the bar sticking out at each pole . Currently, the field's north and south magnetic poles are very near to the Earth's north and south geographic poles.Some iron-bearing minerals, like tiny magnetite crystals in igneous rocks, point to the north magnetic pole as they crystallize from magma. These little magnets record both the strength and direction of the Earth's magnetic field. The direction is known as the field's magnetic polarity. In the 1950s, scientists began using magnetometers to look at the magnetic properties of rocks in many locations.
What is stress in geology?
Enormous slabs of lithosphere move unevenly over the planet's spherical surface, resulting in earthquakes. This chapter deals with two types of geological activity that occur because of plate tectonics: mountain building and earthquakes. First, we will consider what can happen to rocks when they are exposed to stress. Causes and Types of Stress fractured rocks Figure 1. Stress caused these rocks to fracture. Stress is the force applied to an object. In geology, stress is the force per unit area that is placed on a rock. Four types of stresses act on materials. A deeply buried rock is pushed down by the weight of all the material above it. Since the rock cannot move, it cannot deform. This is called confining stress. Compression squeezes rocks together, causing rocks to fold or fracture (break). Compression is the most common stress at convergent plate boundaries. Rocks that are pulled apart are under tension. Rocks under tension lengthen or break apart. Tension is the major type of stress at divergent plate boundaries. When forces are parallel but moving in opposite directions, the stress is called shear. Shear stress is the most common stress at transform plate boundaries.
what factors cause mass wasting
Factors that change the potential of mass wasting include: change in slope angle, weakening of material by weathering, increased water content; changes in vegetation cover, and overloading. Volcano flanks can become over-steep resulting in instability and mass wasting.
what is the plate tectonics theory?
From the deepest ocean trench to the tallest mountain, plate tectonics explains the features and movement of Earth's surface in the present and the past. Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core.
What is a force?
Geologic structures are usually the result of the powerful tectonic forces that occur within the earth. These forces fold and break rocks, form deep faults, and build mountains. Repeated applications of force—the folding of already folded rocks or the faulting and offsetting of already faulted rocks—can create a very complex geologic picture that is difficult to interpret. Most of these forces are related to plate tectonic activity. Some of the natural resources we depend on, such as metallic ores and petroleum, often form along or near geologic structures. Thus, understanding the origin of these structures is critical to discovering more reserves of our nonrenewable resources.
normal dip-slip fault
Hanging wall moves down compared to the foot wall
how do tectonic and gravitational forces affect landscape evolution?
Home Science Encyclopedias almanacs transcripts and maps Landscape Evolution Landscape Evolution World of Earth Science COPYRIGHT 2003 The Gale Group, Inc. Landscape evolution A landscape is the cumulative product of interaction among dynamic geological processes over time. A region's topography and suite of characteristic landforms are, thus, clues to its geologic history. For example, the landscape of rugged, linear mountain chains , deep canyons, dry lake beds, and mesas in the United States'desert southwest tells a geologic story of fluvial and Eolian erosion acting during a period of increasing climatic aridity while plate tectonic forces caused crustal extension and uplift. Earth processes carve a landscape; dynamic interactions between processes control its evolution over time. The earth's internal heat drives plate tectonic motion and influences the related processes of crustal uplift, magmatic intrusion, volcanism, crustal deformation, and seismic activity. External heat from the Sun forces circulation of Earth's atmosphere and hydrosphere, which in turn drives sedimentary processes such as weathering, erosion, transportation, and deposition. These forces, interacting under the influence of gravity , shape Earth's surface. Earth processes interact in complex feedback systems. A change in the rate or directional alignment of one process—for example, an increase in rainfall or the abandonment of a river channel—may start a cascade of compensatory changes throughout a region. Plate-tectonic mountain-building and erosion interact in a negative feedback system that regulates the elevation of continental mountain belts. Elevation interacts with temperature and rainfall, the components of climate , to regulate rates of erosion. Climate interacts with vegetation to create soils. A balance between precipitation and temperature maintains a glacier. These are just a few examples of the dynamic processes that shape a regional landscape, and of the interactions that remold an existing array of landforms over time.
How can you determine which plate will subduct below another? (think density...)
I can't find this one - but I guess the heavier one goes beneath b/c gravity.
daughter products in decay process
In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps (decay chain). For example, 238U decays to 234Th which decays to 234mPa which decays, and so on, to 206Pb (which is stable):
parent products in decay process
In nuclear physics, a decay product (also known as a daughter product, daughter isotope, radio-daughter, or daughter nuclide) is the remaining nuclide left over from radioactive decay. Radioactive decay often proceeds via a sequence of steps (decay chain). For example, 238U decays to 234Th which decays to 234mPa which decays, and so on, to 206Pb (which is stable):
what period did the dinosaurs live in
Jurassic and Cretaceous
What is mantle convection?
Mantle convection is the slow creeping motion of Earth's solid silicate mantle caused by convection currents carrying heat from the interior of the Earth to the surface.
What era did the dinosaurs live in?
Mesozoic Era
relative dating
Method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock
Assumptions of Plate tectonics theory
New plate material is generated at ocean ridges, or constructive plate boundaries, by sea-floor spreading. The Earth's surface area is constant, therefore the generation of new plate material must be balanced by the destruction of plate material elsewhere at destructive plate boundaries. Such boundaries are marked by the presence of deep ocean trenches and volcanic island arcs in the oceans and, when continental lithosphere is involved, mountain chains. Plates are rigid and can transmit stress over long distances without internal deformation - relative motion between plates is accommodated only at plate boundaries.
timescale
Oldest to Youngest: Eras: Paleozoic- 544 - 248 million years ago Mesozoic-248 - 65 million years ago Cenozoic-65 million years ago - Present Periods: Precambrian (Beginning of earth - 544 million years ago) Cambrian (544 - 505 million years ago) Ordovician (505 - 440 million years ago) Silurian (440 - 410 million years ago) Devonian (410 - 360 million years ago) Carboniferous (360 - 286 million years ago) ALSO: Mississippian* (360 - 325 million years ago) Pennsylvanian* (325 - 286 million years ago) Permian (286 - 248 million years ago) Triassic (248 - 213 million years ago) Jurassic (213 - 145 million years ago) Cretaceous (145 - 65 million years ago) Tertiary (65 - 1.8 million years ago) Quaternary (1.8 million years ago - Present)
Why is radiocarbon dating restricted to a range of less than 50,000 years?
Over time, carbon-14 decays radioactively and turns into nitrogen. A living organism takes in both carbon-12 and carbon-14 from the environment in the same relative proportion that they existed naturally. Once the organism dies, it stops replenishing its carbon supply, and the total carbon-14 content in the organism slowly disappears. Scientists can determine how long ago an organism died by measuring how much carbon-14 is left relative to the carbon-12.
Which theory finally convinced geologists that the continents did move?
Paleomagnetism- the branch of geophysics concerned with the magnetism in rocks that was induced by the earth's magnetic field at the time of their formation. - the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. -important source of our knowledge about the Earth's evolution throughout the entire geological history. This record is preserved by many rocks from the time of their formation.
current geologic period
Quaternary
dip-slip fault stress
Stresses that pushed past each other in opposite directions. Deformation in a rock that is due to a stress that exceeds the rock's internal strength. A fault in which the dip of the fault plane is vertical.
How are geomagnetic reversals evidence for plate movement?
The Earth's magnetic field is produced by the flow of liquid iron within its core, three thousand kilometers below our feet. What made researchers think of a link between plate tectonics and the magnetic field? The discovery that convective liquid iron flows play a role in magnetic reversals: experiments and modeling work carried out over the last five years have in fact shown that a reversal occurs when the movements of molten metal are no longer symmetric with respect to the equatorial plane. This "symmetry breaking" could take place progressively, starting in an area located at the core-mantle boundary (the mantle separates the Earth's liquid core from its crust), before spreading to the whole core (made of molten iron). the degree of asymmetry has varied at the same rhythm as the magnetic reversal rate (number of reversals per million years). The two curves have evolved in parallel to such an extent that they can almost be superimposed. In other words, the further the centre of gravity of the continents moved away from the equator, the faster the rate of reversals (up to eight per million years for a maximum degree of asymmetry). What does this suggest about the mechanism behind geomagnetic reversals? The scientists envisage two scenarios. In the first, terrestrial plates could be directly responsible for variations in the frequency of reversals: after plunging into the Earth's crust at subduction zones, the plates could descend until they reach the core, where they could modify the flow of iron. In the second, the movements of the plates may only reflect the mixing of the material taking place in the mantle and particularly at its base. In both cases, the movements of rocks outside the core would cause flow asymmetry in the liquid core and determine reversal frequency.
What is the rate of sea-floor spreading?
The Pacific is also home to one of the world's most active spreading centers (the East Pacific Rise) with spreading rates of up to 13 cm/yr. The Mid-Atlantic Ridge is a "textbook" slow-spreading center, while the East Pacific Rise is used as an example of fast spreading.
What is the Curie point?
The temp in which the magnetic properties of a solid can be changed. This is 350°
reverse dip-slip fault
The wall above the fault plane moves up
What are oceanic trenches and how do they form?
Trenches are formed by subduction, a geophysical process in which two or more of Earth's tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression.
What is a strain?
When stress causes a material to change shape, it has undergone strain or deformation. Deformed rocks are common in geologically active areas.
Monocline
a bend in rock strata that are otherwise uniformly dipping or horizontal.
lahar
a destructive mudflow on the slopes of a volcano.
dome
a feature in structural geology consisting of symmetrical anticlines that intersect each other at their respective apices. Intact, domes are distinct, rounded, spherical-to-ellipsoidal-shaped protrusions on the Earth's surface
index fossil
a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found
basin
a natural depression in the surface of the land often with a lake at the bottom of it
Anglular unconformity
an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers. The whole sequence may later be deformed and tilted by further orogenic activity.
Anticline
an upward fold in rock formed by compression of Earth's crust
absolute dating
any method of measuring the age of an event or object in years
largest mass extinction
at the end of the Permian Period
which type of soil is most stable: loose gravel, sand, or clay?
clay
slowest moving event in mass wasting
creep
Role of water in mass wasting (increase or decrease cohesive strength)
decrease cohesive strength
What is strike in geology
direction of the line formed by the intersection of a fault, bed, or other planar feature and a horizontal plane. Strike indicates the attitude or position of linear structural features such as faults, beds, joints, and folds.
Noncomformity
exists where sedimentary rock layers lie on top of an eroded surface of nonlayer igneous or metamorphic rock
how often do magnetic reversals happen?
in the last 10 million years, there have been, on average, 4 or 5 reversals per million years
fast moving event in mass wasting
mudflow
Is the sea-floor spreading centers relatively older or younger than the spreading farther away from the center?
older are found farther away
What is a horst and a graben?
refer to regions that lie between normal faults and are either higher or lower than the area beyond the faults. A horst represents a block pushed upward relative to the blocks on either side by the faulting, and a graben is a block generally long compared to its width that has been lowered relative to the blocks on either side due to the faulting. Horst and graben are formed when normal faults of opposite dip occur in pair with parallel strike lines. Horst and graben are always formed together. Graben are usually represented by low-lying areas such as rifts and river valleys whereas horsts represent the ridges between or on either side of these valleys.
8 types of mass wasting
rock fall rock avalanche slides slump flows debris flow earth flow creep
what type of rock samples are used for radiocarbon dating
sedimentary rocks (have to have c14 aka carbon)
in what kind of structure are oil and natural gas often trapped?
sedimentary rocks- Shale, Sandstone The types of rocks that contain oil and natural gas are all sedimentary rocks, rocks formed when grains and mineral particles deposited by running water fuse together. Because these rocks are cemented together from such small components, they are porous, full of spaces in which energy-rich carbon compounds can settle, later to be liberated in the form of either oil or gas.
where does the water on mt st helens come from
spirit lake
Principles of Relative Dating
super position, Original Horizontality, Lateral Continuity, Cross-Cutting, Inclusions, Fossil Succession
what is dip in geology
the angle at which a planar feature is inclined to the horizontal plane; it is measured in a vertical plane perpendicular to the strike of the feature. Plunge is the vertical angle between the horizontal plane and the axis or line of maximum elongation of a feature. Plunge is measured along the axis of a fold, whereas dip is measured along the limbs. Pitch is the angle between the axis of the feature and the strike of the plane containing the axis.
mass wasting
the downslope movement of rock, regolith, and soil under the direct influence of gravity
What are geomagnetic reversals?
the earth's magnetic north and south change. they do a flip :)
What is sea floor spreading?
the formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side.
continental drift
the gradual movement of the continents across the earth's surface through geological time.
angle of repose
the steepest angle at which loose material remains stationary without sliding downslope
half-life
the time taken for the radioactivity of a specified isotope to fall to half its original value. A radioactive half-life refers to the amount of time it takes for half of the original isotope to decay. For example, if the half-life of a 50.0 gram sample is 3 years, then in 3 years only 25 grams would remain.
thrust dip-slip fault
thrust fault is a reverse fault with a dip of 45 degrees or less.
Disconformity
unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition.