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EARTH SCIENCE FINAL EXAM 85
Questions and Answers
List the 3 main layers of the earth from the center to the outside based on composition (what they are made out of). - ✔1). Core (Inner and outer)-solid inner liquide outer. Iron/nickel alloy. Extreme pressure 2).Mantle-82% of the earth's volume-Solid, rocky, shell 3). Crust (Oceanic-younger rocks and Continental-granite rocks) List the 5 mechanical layers of the earth (based on how they deform?) Whic layers is a liquid? - ✔1.The lithosphere is the outermost mechanical layer and is the most rigid layer of the Earth. The lithosphere consists of the crust, and some of the uppermost mantle. The lithosphere averages about 100 km thick. It is somewhat thicker beneath continents, and dramatically thinner under mid-ocean ridges. 2.The asthenosphere lies beneath the lithosphere. It is a part of the mantle, approximately 100 km thick, with very little strength. The asthenosphere flows relatively easily and accomodates the movement of the overlying lithosphere. The upper and lower boundaries of the asthenosphere are diffuse as they involve gradual changes in the rigidity of the mantle, not a change in composition. 3.The lower mantle or mesosphere consists of most of the mantle. This part of the mantle flows, but at much slower rates than the asthenosphere. 4.The outer core is liquid iron (with some nickel and other elements). This is the only internal layer of the Earth that is a true liquid. The core-mantle boundary is the one mechanical boundary that is also a compositional boundary. Movement of the electically conductive fluid in the outer core generates the Earth's magnetic field. 5.The inner core is solid. It has the same composition as the outer core, and is about half the diameter of the core. What were four pieces of evidence that Wegener used in 1912 to support his theory of continental drift? - ✔1). Jigsaw fit of continents 2). Fossil Coninuity 3).Ancient Glaciations Match
4).Mountain Ranges Match What did Wegener's Theory lack (what did he get wrong)? - ✔How the continents moved. Did not have a logical answer to this. He felt... What is seafloor Spreading and what is the evidence of this? - ✔New oceanic crust form at spreading center-Age of seafloor increases as you move away from the ridge. Evidence: 1).Paleomagnetism (magnetic pattern of seafloor)-Matching polarities on either side of ridge show that all oceanic crust formed at ridge 2). Magnetic Reversals&Age Bands: Seafloor spreading in past 180 my shown by symmetrical bands of relative rock age and magnetic polarity on either side of ridge. Describe the lithosphere in detail?What layers of the earth make it up? Is it solid or liquid? How does it deform (by flowing or by breaking)? - ✔Lithosphere (sphere of rock)=the plates=all of the crust and the upper most part of the mantle. Brittle solid-deforms by breaking. Moves around on the top of the astenosphere Describe the asthenosphere in details? In waht layer of the earth is it contained? Is it solid or liquid? - ✔Astehnsophere (weak sphere)-plastic solid-deforms by flowing. This is where warm material rises up and cooler material sinks-convection that drives the plates apart and together. Summarize the theory of plate tectonics. - ✔Plate Tectonics Theory- states that the lithosphere is divided into ~30 rigid plates that are slowly moving about the surface of the planet from forces within (asthenosphere) the Earth. The plates may move together, apart or slide past each other. Types of stress that causes deformation of rocks. - ✔Pushing together (compression); Pulling apart (Tensional); Shear (slide past each other. What is the divergent boundary: What features are formed there? Draw One. - ✔A boundary at which two plates move apart.
- Divergent-Mid Ocean Ridge - Oceanic-Oceanic 2).Divergent-Continental Rift-continental/Continental
What is the Volcanic Island Arc - ✔A chain of volcanic islands generally locates a few hundred Kilometers from a trench where subduction occurs. Earthquakes:Chapter 8 - ✔ What is the difference between an earthquake focus and epicenter and fault? Draw a picture to show the difference. - ✔Fault-break in the crust of the earth along which movement has occurred. Focus-The source of the earthquake-where the earthquake originates. Epicenter-The location on the Earth's surface directly above the focus of an Earthquake. Understand the difference between a fault, earthquake focus, and epicenter. Fault-break in the crust of the earth along which movement has occurred. Focus-The source of the earthquake-where the earthquake originates. Epicenter-The location on the Earth's surface directly above the focus of an Earthquake. Where do most earthquakes occur (center of plates or at the edges (plate boundaries)?
✔They usually occur when rocks under stress suddenly shift along a fault (break in the crust of the earth along which movement occurred). What is the Elastic Rebound Theory? - ✔The rocks on each side of a fault are moving slowly. The fault doesn't move due to friction-the stress in the rocks increases and they bend. Stress overcomes friction=blocks move on either side of fault move (unlocked). The rocks then rebound (snap) back to their original shape but in a new position. The rebound/snap releases energy as seismic waves. What are the deep-focus earthquakes and where do they occur (specific type of plate boundary)?Why are they only found at this type of boundary? - ✔ Make a table that summarizes P,S, and surface waves. - ✔1). P WAVES (Primary)
- Fastest moving waves (high frequency)
- First to be recorded by seismographs
- can travel through both solids and liquids through the earth
- Longitudinal or compressional waves
- They are longitudinal waves0cause rock particles to move in the same direction the wave (energy is traveling) 2). S WAVES (Secondary)
- Travel slower than P waves
- can only travel through solids
- S waves are transverse waves or shear waves
- They cause rock particles to move at right angles to the direction in which the wave (energy) is traveling 3). SUFRACE (L) WAVES
- Slowest waves, last to reach a seismograph station
- Can travel like ocean waves along the earth's surface
- surface waves cause the outer layer of the Earth to rise and fall
- Surface waves cause the most damage *Damage is reduced in deeper focuses quakes. Describe how earth scientists locate an epicenter. - ✔The difference in speeds of P & S waves provides a way to locate the epicenter. The formula given distance between P&S waves and Max Amplitude is: The greater the interval between the arrival of the first P wave and the First S wave-the greater the distance to the earthquake epicenter. What is a wave/transverse wave/longitudinal wave? - ✔1). Wave-A disturbance in a medium (the material the wave travels through) that transmits energy but not matter. 2).Transverse Wave: A wave in which the medium moves at right angles (90 degrees) to the direction the wave moves. 3). Longitudinal Wave-a wave in which the medium moves in the same direction as the wave. Review use of travel time graphs: 1). If a p-wave arrives as a seismograph station 5 minutes after an earthquake happened how far away is the epicenter. 2). If an s-wave arrives 6 minutes behind a p-wave at the same seismograph station how far away is the epicenter? - ✔
How can earthquakes of the same magnitude have much different results in terms of destruction and death? - ✔If they occur in a highly populated area versus one that does not have a lot of people (remote villages vs cities). Code of construction in the area it stikes-poorer third world countries versus more sophisticates and wealthier areas with strong building codes. Is the mantle a solid or a liquid? How would we know? - ✔Solid-we know because S waves travels through the mantle and they can only travel through solids. VOLCANOES: Chapter 10 - ✔ What is a hot spot and how does it form a chain of islands like the Hawaiian Islands" How is magma generated at a hot spot? - ✔Hot spots (not at plate boundary)- high heat flow from outer core causes melting in the mantle Hot spots in the mantle can cause melting of the crust within a tectonic plate. Hot spots remain stationary in the mantle, but the lithospheric plate moves across it. The volcano on the surface is eventually carried away from the hot spot and becomes inactive. A new volcano then forms where new crust has moved over the hot spot. (Yellow Stone) What is the Ring of Fire? - ✔Volcano belt that rims the Pacific ocean Describe Felsic, intermediate, and mafic lava. - ✔Mafic- 45 - 55% SiO2 Content-Basaltic Magma type-High Temps (1000-1200C)-Low Viscosity. Intermediate 55-65% SiO2-Andesitic Magma Type- 800 - 1000 C-Intermediated Fiscosity Felsic- 65 - 75% SiO2 Content-Rhyolitic Magma Type- 650 - 800C-High Viscosity How does magma type control eruptive style? - ✔eruption?
1). Viscosity (whether the magma is thick and sticky or thin an runny-a substance's resistance to flow). - Maple Syrup is more viscous than water-flows more slowly. The more viscous the magma the more explosive the eruption. 2). Dissolved Gases (mostly water vapor and carbon dioxide). Eruptions of fluid balsaltic lava-quiet. Highly viscous magma-slow upward movement of expanding gasses- explosive. Due to its Viscosity-Mafic Magma-lower Viscosity-less intense eruptive style. Intermediate - More intense eruptive sytle Felsic-High Eruptive Stled Where (plate settings) is each magma type found? Why? - ✔Divergent Boundaries- (and hot spots under oceanic crust)-lowest % of silicon and oxygen. Mafic composition. Basaltic Magma type lower viscosity. Less intense eruptive style. Subduction Zones (Ring of Fire). Intermediate Silicon and oxygen. Mixture of oceanic and continental. Magma type Andesitic-intermediate Viscosity. More intense eruptive style. Hot Spot under continental crust (Yellowstone)-highest % of silicon and oxygen. Felsic composition/Rhyolitic Magma Type/High eruptive style. What is a pyroclastic flow? On what kind of volcano do they occur?Why are they so dangerous? - ✔Composite Volcanoes: Intermediate ex. Mount St Helens, Mt Fuji, Mt Hood Pyroclastic Flow: Alternating layers of lava and pyroclastic flows Silica-rich magma with andesitic composition (high viscosity) Often tall & steep (due to stickier lava and pyroclastic material) Explosive eruptions - may destroy part of volcano Gas, rocks and other volcanic debris speeds downhill after an eruption
✔). Temperature-the cooler the more viscous (lava cooled hardens doesn't flow).
- Chemical composition (most important)-the more silica in magma the greater the viscosity-erupts more explosively. Where, in general, are most volcanoes located? - ✔Most are located along divergent and convergent plate boundaries. Some volcanoes form far from plate boundaries above hot spots in the crust. Can scientists accurately predict volcanic eruptions?What methods are used to monitor volcanoes and attempt to warn the populations living near the volcano? - ✔1). Use seismographs to monitor small earthquakes. this indicates growing pressure on the surrounding rocks as magma works its way upward. 2). Use surveying with lasers and GPS to detect a slight bulging of the surface of a volcano. 3). Changes in the gases given off by a volcano. 4). Knowledge of previous eruptions. Describe the anatomy (make up) of a volcano. - ✔volcano. 1). Volanic activity begins when a fissure (crack) develops in the crust as magma is forced to the surface. 2). Magma collects in a pocket=magma chamber. 3). gas rich magma rises from magma chamber - travels through circular pipe and reaches surface at a vent. 4).Repeated eruptions of lava or pyroclastic material eventually build a volcano. 5).Located at the summit of many volcanoes is a steep depression called a crater. Earth History - ✔ What is the PRinciple of Uniformitarianism?How is Uniformitarianim different from Catastrophism? - ✔Uniformitarianism: When: late 1700's Idea: Earth is very old and the same processes that operate today haveoperated throughout Earth's long history. "The present is the key to the past." Based on: scientific thinking Example: Grand Canyon was carved slowly by the river eroding its bed over 10's of thousands of years (slow processes if given enough time can cause major changes to Earth's surface Widely Accepted theory
Catastrophism: When: 1600 to 1700 Idea: Earth is young (only a few thousand years old) and the features of the earth were created by great catastrophes Based on: Belief Example: Grand canyon formed in a matter of months from a huge flood that happened in the past - floods like this no longer occur Not the accepted theory Understand how each of the following can be used to sequence a stratigraphic column: laws of relative dating, zone of contact metamorphism,igneous rocks,metamorphic rocks,sedimentary rock layers,unconformities. - ✔1) Relative Dating: method that uses a set of principles to sequence geologic events (indicates that one layer is older or younger than another layer) Relative Age - tells you the timing of an event compared to other events in a sequence but not exactly when it happened 2).Unconformities - represent a period of geologic time for which there is no rock record (due to deposition stopping or weathering and erosion removing rock) in a specific area. 3).Sedimentary rocks deposited and lithified (underwater) Uplift of land or sea level drop exposes rocks on surface of continent Weathering and Erosion removes upper layers of rock Subsidence (sinking) or sea level rise puts rocks below sea level again More sedimentary rocks are deposited (form) on top of old erosional surface What is an unconformity? What does an unconformity represent in the geologice record? - ✔- Unconformities are surfaces that represent a gap in the geologic record. Sediment was not deposited or weathering and erosion have removed rock layers. Unconformities - represent a period of geologic time for which there is no rock record (due to deposition stopping or weathering and erosion removing rock) in a specific area. What is the difference between absolute and relative dating? - ✔Relative Dating: method that uses a set of principles to sequence geologic events (indicates that one layer is older or younger than another layer) Relative Age - tells you the timing of an event compared to other events in a sequence but not exactly when it happened
ratio in a sample Ex. After 2 half-lives, the amount of parent isotope remaining is ¼ The amount of daughter product formed is ¾ The age of the sample is calculated: 2 half life's X 5700 years = 11,400 yrs ANSWER: How old do most geologists think the Earth is? - ✔4.6 Billion Years What are fossils? What are the different types? - ✔Fossils are remains of ancient living things or traces of activity. I). BODY TYPES: entire organism preserved. A). Petrification: Groundwater removes the original organic materials and replaces them with new materials B). Molds: Impressions of an organism. C). Casts: Formed when sediment fills a mold and hardens. II. TRACE FOSSILS: Tracks, footprints, gastroliths, borings, burrows,feces. Types of preservation: 1). Amber (rare)-Amber is hardened tree sap. Insects become trapped in the sticky sap and then it hardens. 2).Tar Seeps (rare)-Tar seeps are formed by thick petroleum oozing to the surface. Animals are sometimes trapped and then preserved the tar. 3). Ice-Human remains found in Italian Alps. What are Index Fossils and what are their characteristics. - ✔Index fossils are:
- widespread around the Earth
- easily identifiable
- from species that lived for a short span of geologic time
- Abundant (easy to find) Used to correlate rock layers and assign ages to specific rock layers In what type of rock are most fossils found (igneous, sedimentary, or metamorphic)? WHy? - ✔Fossils are typically found in sedimentary rock, almost all of which were originally deposited as sediments by moving water. Subsequent processes hardened them into sedimentary rock, as overlying pressure squeezed the water out and the grains were cemented together. What conditions favor fossil preservation? - ✔1). Hard parts 2). Quick burial 3). Most are marine invertebrates
- Complete organisms are extremely rare. What is the geologic time scale and how is it organized? - ✔The division of Earth history into blocks of time. - eons, eras, periods, and epochs. Scale created by using a relative dating principle. Earth is 4.6 billion years old. We know this through geology (rocks/fossils). What are the major divisions of geologic time? - ✔Eons/Eras Periods What major events mark the boundaries between eras of geologic time? - ✔Major evens such as Mass Extinctions mark the boundaries between eras of geologic time. In general, how has life changed on this planet with time? (not changed much, more complex with time, less complex with time)? - ✔ WATER CYCLE AND RIVERS: CHAPTER 6 - ✔ Draw a diagram of the water cycle. Know all of the main reservoirs and processes (evaporation, condensation, etc) that move water from one reservoir to another. -
Gradient: Low and V is slow Channel Size: Large V Fast Channel Shape: Deep semicircle V Fast Channel Roughness: Low-Smooth V Fast Discharge: High V Fast OVERALL FAST. Downcutting = V Shaped Valley Meandering=Wide Valley. What is the mouth of a river?What iar the headwaters of a river? - ✔Headwaters - source area for a river (start of the river) Mouth - end of river (where it empties into a larger body of water) What is a watershed/drainage basin? What is a divide? - ✔Watershed-The area of land that drains a long a certain point along the river. Divide- an imaginary line that separates the drainage of two streams; often found along a ridge What is meant by the discharge of a river? - ✔Discharge - is a volume of water moved through the stream per time (e.g. gallons per second) What is a stream loan? What are the 3 types of stream loads? - ✔Stream load - sediments carried by a stream 1).Dissolved Load - Dissolved ions from minerals, can not be seen (ions: Na+, Cl-, Ca2+, CO32-) 2).Suspended Load - speed of the water keeps these particles suspended off bed; Can be seen = Muddy appearance 3).Bed Load - coarse sand, gravel, and pebbles; moves by sliding, rolling, or short jumps called saltation. What are the major controls on the velocity of water in a river? - ✔The ability of a stream to erode and transport material is directly related to the VELOCITY (speed of the stream, cm/s) of the water in the channel. 4 Factors influence stream velocity: Gradient Discharge
Size and shape of channel Roughness of channel bed Where (near the headwaters or the mouth) do rivers meander? Why? - ✔Meaner is a loop in the river. Where?? Why?? Know the formula for calculating the gradient between two points on a river. Where along the longitudinal profile of a river is the gradient steep? Gentle? - ✔??? (Gradient steep near headewater). What are floodplains and how do they form? - ✔It is the flat, low lying portion of a stream valley subject to periodic flooding. Overflowing of the river. GROUNDWATER: 6.3 - ✔
