Midterm ESC
Describe the differences between the lithosphere and asthenosphere (include depth and mechanical behavior of each)
Lithosphere: the crust and upper mantle; 100-150km thick, behaves rigidly Asthenosphere- lower mantle; lies beneath the lithosphere, flows at rates of 1-15cm/year, behaves plastically (100-250 km) beneath Earth's surface.
Describe how what is now Florida became part of the North American continent during this evolution
Refer to Plate Tectonic 3: 6:40-11:15
Apply the concept of isostasy to processes that change the crustal thickness (i.e., explain the response of the elevation of the Earth's surface and the crust/mantle boundary (Moho) during crustal thickening or thinning by erosion
-- Lower density crust floats on higher density mantle. -Areas with thicker crust have higher elevation on land and go down deeper into the mantle (called crustal root). For every 5-6 km crustal thickness increase, the elevation of land surface increases by 1km and depth of moho decreases by 5-10 km depth changes because as elevation changes with erosion Erosion: Reduction in crustal thickness→ surface elevations decrease and crustal/mantle boundary (moho) raise up.
Compare the difference in ground motion with increasing magnitude earthquakes using the Richter scale (e.g., how much more ground motion in a magnitude 4 vs. a magnitude 3?; a magnitude 6 vs magnitude 3?)
-An increase of one unit of magnitude represents a tenfold increase in the maximum amplitude of ground motion. -A magnitude 4 earthquake results in a ground motion that is 10 times greater than that of a magnitude 3. -A magnitude 6 earthquake results in a ground motion that is 10^3 times greater than a magnitude 3 earthquake
List the three types of convergent boundaries
-Continent-continent: Mountain Building -Continent-ocean: Continental Arc -Ocean-ocean: Island Arc
Identify the igneous composition that most closely represents the overall composition of the continental crust, oceanic crust, and mantle
-Continental Crust: felsic Granitic with 25-45% dark minerals (granite and rhyolite) Intermediate Andesitic (Andesite) -Oceanic Crust: 45-80% dark minerals Basaltic mafic (Gabbro and basalt) -Mantle: 85-100% dark minerals mafic
Explain how continental shelves and rises/slopes are produced during this evolution
-Continental shelf: extends from the coastline of a continent to a drop-off point called the shelf break. From the break, the shelf descends toward the deep ocean floor in what is called the continental slope. ---Formed by sediment accumulating along a passive margin Continental slope: the slope between the outer edge of the continental shelf and the deep ocean floor.- Continental rises: A gentle slope under the cont. slope. Most sediment settles here because the cont. slope is so steep.
Describe the difference between the dark (ferromagnesian) and light (non-ferromagnesian) silicate minerals
-Dark silicate materials have iron and/or magnesium in their structure and are more- Light, or non-ferromagnesian silicate materials have no iron or magnesium and are less dense
Explain each of the three changes that are capable of causing rocks to melt
-Decompression (decrease in pressure on rock)-Addition of volatiles (water and Co2)-Conduction (heating)
List the material that may be present in these pyroclastic eruptions
-Gas-Ash-Pumice-Hot lava blocks
List and explain the five criteria used to define a mineral
-Naturally occurring: Real minerals form in nature- Homogeneous: Ideally, a piece of a mineral has the same composition and structure throughout -Solid: Liquids (such as oil or water) and gases (such as air) are not minerals. -Crystalline solid: If the atoms in a material are not distributed randomly, but rather remain fixed in a specific, orderly pattern, we can refer to the material as a crystalline solid. All minerals have this characteristic. The internal architecture of a mineral, simplistically, resembles a grid of scaffolding.- Definable chemical composition: This phrase emphasizes that a given mineral contains specific elements in specific proportions.
Describe the difference between Plinean-style eruptions and pyroclastic flows.
-Pilinian: Large explosive events that form enormous dark columns of tephra and gas high into the stratosphere -Pyroclastic: A fast-moving current of hot gas and volcanic matter that flows along the ground away from a volcano at high velocities
Use a map of the age of the ocean floor to assess:-Rates of spreading at mid-ocean ridges - Age of continental break-up or separation
-Refer to questions 10, 14, 15 of Assignment 1 -Refer to questions 11, 16, 17 of Assignment 1
Explain the difference between relative and absolute motion of tectonic plates
-Relative Plate Velocity: how far a plate moved compared to another plate that is also moving---The rate and direction of movement of a lithospheric plate with respect to another lithosphere plate. -Absolute Plate Velocity: how far a plate moved from a fixed position---the movement of a plate relative to a fixed reference point in the mantle, such as a hotspot,
Calculate the directions and rates of plate motion using: age of the seafloor map and magnetic anomalies formed at mid-ocean ridges, hotspot volcanic tracks, magnetic inclinations (apparent polar wander paths)
-To calc avg rate at which a point moves away from the ridge axis divide the scale (given in km at bottom) by the give (Ma) use the magnetic reversal time scale to identify age of oceanic crust. Refer to questions 18, 19, 20 of Assignment 1 -Use triangles to tell direction (Distance=rate X time) a hotspot track on a plate moving over a mantle plume provides a record of the plates rate and direction of movement. Track it leaves behind is indicative plate motion over the hotspot but the hotspot stays stationary. Refer to questions 22, 23 of Assignment 1
Explain what is meant by "flood basalts" and identify the geologic feature they are associated with
A flood basalt is the result of a giant volcanic eruption (mafic?) or series of eruptions that covers large stretches of land or the ocean floor with basalt lava flood basalt may form where a rift develops above a continental hot spot. Almost entirely basalt, only local subaqueous conditions, each one was formed in less than a million years.
Explain the difference between hypothesis and a scientific theory
A hypothesis is a possible explanation for an observed situation. A scientific theory is supported by evidence. If you test a hypothesis hundreds or thousands of times and it is correct every time then it will become a scientific theory. A scientific theory has passed many tests and has, so far, failed none
Explain what is meant by a ""lahar"" and list multiple ways they may form
A lahar is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water The material flows down from a volcano, typically along a river valley can occur even when a volcano isn't actively erupting. result when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels.
List a present-day and "fossil" example of continent-continent collision.
A modern zone of continental collision is the Himalayas from Indian plate colliding with the Asian plate Ancient: Namibia or Appalachians from North American plate colliding with African plate
Describe what is meant by data
A set of measurements, calculations, or observations that give us clues to help answer a problem
Explain what is meant by a testable hypothesis
A testable hypothesis is a hypothesis that can be proved or disproved as a result of testing, data collection, or experience. Only testable hypotheses can be used to conceive and perform an experiment using the scientific method.
Explain how the time lag between the arrival of the first P-waves and the first S-waves can tell you the distance to an earthquake and explain the steps used and data necessary to locate the epicenters of earthquakes
AS P and S waves travel out from an earthquake, P waves get progressively farther ahead. Therefore, the farther a seismic recording station is from the earthquake epicenter, the greater the difference in time of arrival between P and S waves. To locate the epicenter of an earthquake, seismic data is collected from at least three locations (called triangulation) to determine the epicenter from where it intersects
Describe how crust may be accreted to the edges of continents
Accretion is a process by which material is added to a tectonic plate or a landmass. This material may be sediment, volcanic arcs, seamounts or other igneous features. as subduction takes place, seafloor sediment as well as sand and mud that wash into the trench from nearby land get scraped up and incorporated into a wedge-shaped mass
Describe what is meant by the geosphere, hydrosphere, atmosphere, and biosphere
Atmosphere- layers of gases surrounding Earth (clouds, ozone) Hydrosphere- all water (surface water-glaciers, oceans, snow, and groundwater-open holes, cracks underground) Biosphere- all living organisms on Earth (land surface, hydrosphere, upper geosphere, and lower atmosphere) Geosphere- layers of crust of Earth (crust, mantle, outer core, inner core)
Explain why the seafloor on one side of the transform boundary may be higher, despite the fact that the motion is horizontal
Because buoyancy is based on temperature and distance from ridge (hotter equals higher) then sinks as they cool
Explain the differences between the crust, mantle, and core and the position of each within the Earth. Describe the processes that formed these layers.
Because the Earth was a liquid, the densest materials were able to sink to the core and the least densest materials floated to the top near the crust. Planetesimals are originally homogeneous but as it grows gets warmer on the inside. Interiors of planetesimals containing refractory materials become so hot they melt internally producing droplets of molten iron alloy These droplets were denser than the rocky material around them, so they sank downward due to the inward pull of gravity and accumulated into the core. Remaining materials formed a shell called the mantle surrounding the core. By the process of differentiation Earth developed internal layers. Crust: makes up less than 1 percent of Earth by mass consists of oceanic crust and continental crust is often more felsic rock. Made up of basalt and gabbro Mono: crust-mantle boundaryry Mantle: Hot and represents about 68 percent of Earth's mass. Consists entirely of periodite. Seperated into a lower and upper mantle (separation is the transition zone). The upper mantle, the lithosphere is rigid, and the lower mantle, the asthenosphere is hot and has plasticity. Core: Mostly iron metal Makes up about 31% of the Earth. Core is an iron alloy (composed of 2 or more metals), outer core is molten, and the inner core is solid. Flow within the core causes our magnetic field!
Explain the relationship between mineral grain size and cooling rates for coarse-grained, fine-grained, porphyritic, and glassy textured igneous rocks
Because the body loses heat to its surroundings only at its surface, bodies with a large surface area per unit volume cool faster. -Coarse-Grained: grains large enough to see with naked eye, forms during slow cooling (more atoms would grow a larger grain), atoms diffuse through magma and come to sight where minerals crystallize- Fined-Grained: Individual mineral grains are present but are too small to be seen with naked eye. Forms during rapid cooling (so there is not enough time for atoms of different elements to be added). -Porphyritic Texture: large grains embedded in a matrix of smaller grains. Slow cooling followed by rapid cooling. -Glassy Texture: no mineral grain forms because there is no internal arrangement of atoms. Forms from instantaneous cooling (quenching).
Describe the difference in the motion produced by P-waves and S-waves, and two types of surface waves. Include the vibration (or particle motion) compared to wave propagation direction.
Body waves: Pass through earths interior- cause rocks to vibrate in two ways: P and S waves --P waves: aka compressional/ Primary waves, cause back and forth vibrations parallel to the wave movement (think of a spring being pushed together than released) --S waves: aka shear waves, cause up and down vibrations perpendicular to wave movement (think of a rope being whipped up and down). Surface waves: travel along earths surface --R waves: aka Rayleigh waves, go up and down. --L waves: Aka love waves, shimmy back and forth like a snake. *p waves most fastest, then s waves, then surface waves.
Describe the stages of evolution that lead to continent-continent collision
Continent - Continent convergence, Begins as ocean-continent convergence then the Ocean basin closes - continent enters subduction zone, Continents cannot subduct - too buoyant (low density), Two continents collide (continental collision), Collision causes crust to shorten in horizontal direction and therefore thickening in vertical direction Result: large mountain belts, such as Himalayas --2 plates converge, all oceanic crust is subducted because it is less dense. When continental crust converges, it is too dense to subduct, so it pushes upward forming mountains
Explain the difference between active and passive continental margins
Continental margins are the boundaries between ocean basins and continents! Active- a plate boundary is located on the edge of a continent ex- west coast of north America- earthquakes occur here, because fault can occur Passive- the plate boundary is out in the ocean at a distance from the edge of a continent ex east coast of north America- earthquakes do not occur here
Describe the types of information used in assessing an earthquake magnitude using the Modified Mercalli intensity scale
Define quake intensity by assesing the damage it caused and peoples perception of it. -Intensity is I-XII, where the lowest (I) is only detected by seismographs and the highest (XII) causing mass destruction.
Explain how each of these processes (that make rocks melt) occurs at each of the three tectonic settings where magmas are produced (divergent boundaries, convergent boundaries, & hotspots)
Divergent boundaries- decompression- causes plates to seperate- rifting movement causes bouyant magma below to rise and fill in space. Convergent boundaries- addition of volatiles Hotspots- conduction- pressure on rocks in upper mantle just below plate boundary drops- pressure drop lowers rock melting temp because the rock is already hot- they melt, forming magma Hotspots: a region deep within the Earth's mantle from which heat rises through the process of convection. This heat facilitates the melting of rock. The melted rock, known as magma, often pushes through cracks in the crust to form volcanoes
Identify the types of margins at which lithosphere is created, destroyed, or conserved
Divergent: Plates move away from each other and new oceanic lithosphere forms. Convergent: Plates move towards each other and a downgoing plate sinks below it in a process called subduction.- destroys the crust in the lithosphere Transform: One plate slips horizontally against another.-- lith is conserved
Explain the patterns of the distribution of earthquakes around the Earth and the relationship between these patterns and plate tectonics
Earthquakes occur in seismic belts, which correspond to plate boundaries. The increased interactions between boundaries cause an increase in the frequency of earthquakes. Strong earthquakes are more common at transform and convergent boundaries
Explain the characteristics of elastic strain and how, according to the elastic rebound theory, sudden slip on a fault may cause an earthquake
Elastic rebound theory: "elastic deformation" refers to a change in shape that can be reversed by the removal of stress -- think of bending a stick, then releasing that tension-- if you do not relax that tension, the rock will break and the fracture will become a fault. When relaxation takes places, it springs back and forth on the fault, which is known as seismic waves.
Define a fault, epicenter, focus (or hypocenter), and fault scarp
Fault: A planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movement Focus: Aka hypocenter, of an earthquake is where the seismic waves begin. Epicenter: the point on the surface of the earth, on maps, that lies directly above the focus (or start of earthquake). Fault scarp: A small step on the ground or offset on the surface of the Earth. This happens when one side of a fault moves vertically compared to the other side
Explain the environments where each of the igneous rocks textures listed above form
Formed when igneous rocks come to the surface in a process called extrusion Explanation:-At top of the earth's layers with extrusive igneous activity is glassy→ fine-grained→ Porphyritic texture→ coarse-grained where intrusive igneous activity happens. (Intrusive or plutonic rocks crystallize from magma beneath the earth's surface. Extrusive or volcanic rocks crystallize from lava at the earth's surface.)
Describe the characteristics that make pyroclastic flows extremely dangerous and destructive
Hot gas and suspended particles that move along a surface due to density. Hot lava travels at 200km/hr with deposits exploding up to 100 km from source. Can wipe out a town-Fast moving-Hot gas
Explain the differences between temperatures and physical characteristics of mafic and felsic lava flows
Hot lavas are more fluid, while cool lavas are more viscous. High silica, low temperature lavas are most vicious and all the greatest amount of pressure to build up before they "let go" in an eruption. In contrast, lavas that are hot and low in silica are the most fluid. Because basaltic (mafic) lavas are less viscous, they produce relatively gentle eruptions, while volcanoes that erupt felsic lavas (rhyolite and andesite) tend to be more explosive. -Mafic: Forms oceanic crust: hot, they flow easily outward from the vent (where it comes out of the ground), and may travel great distances before completely solidifying. contain more dark, magnesium and iron rich mafic minerals, such as olivine and pyroxene. -Felsic: Forms continental crust: are not as hot, high in silica and volatiles, and have a high viscosity. lighter colored minerals such as quartz and orthoclase feldspar
Describe the scientific method
Identifying the problem, collecting data, proposing hypothesis, testing hypotheses, draw conclusion, share results
Describe the criteria used to predict volcanic eruptions
Imminent eruptions can be predicted by earthquake activity (small explosions), changes in heat flow (increase of hot magma), changes in the shape of the volcano (bulge), and emissions of gas and steam. -- Reccurance intervals predict the average time between eruptions . --A volcanic hazard map shows areas that lie in potential hazard areas.
How do the inner planets (including earth) differ from outer planets in terms of size and composition?
Inner four terrestrial (earthlike) planets, smaller and rocky-Mercury-Venus-Earth-Mars Outer four Jovian planets, larger and gaseous-Jupiter-Saturn-Uranus-Neptune
Describe relationship between surface elevations and crustal thickness in terms of isostasy
Isostasy is the vertical movement of the crust to attain buoyancy in the mantle. This depends on density and thickness. The Earth's crust is less dense than the underlying mantle. For every 5-6 km of crustal thickness land elevation increases by 1 km and depth of moho decreases by 5-10 km depth changes because as elevation changes with erosion we must compensate for this change Refer to Plate Tectonics 6
Describe the process of liquification (or liquifaction)
It takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking The sediments become saturated with water and in turn take on mud like properties If cracks open up between the liquid sand layer and the ground, pressure caused by the weight of overlying sediment squeezes the wet sand up and out, building sand volcanos. Can also result in the formation of fissures and pits
After small solids began to condense in the disk around the sun, how did this material form planets?
Material (such as ice and dust) left in the protoplanetary disk allowed our planets to form through gravity pulling them together, eventually forming plantesimals. If they attracted more material, they could eventually become protoplanets. Finally, in the last stage, large collisions and heavy bombardment like meteor strikes helped make a proper planet.
Describe the generalized topography (elevation profile) of Mid-ocean ridges and rift valleys
Mid ocean ridges: end at "fracture zones" in basins, where there are vertical/right angle fractures. The massive mid-ocean ridge system is a continuous range of underwater volcanoes that wraps around the globe like seams on a baseball It stretches nearly 65,000 kilometers The majority of the system is underwater, with an average water depth to the top of the ridge of 2,500 meters Mid-ocean ridges occur along divergent plate boundaries, where new ocean floor is created as the Earth's tectonic plates spread apart As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt The speed of spreading affects the shape of a ridge - slower spreading rates result in steep, irregular topography while faster spreading rates produce much wider profiles and more gentle slopes. Rift valley: A rift valley is a lowland region that forms where Earth's tectonic plates move apart, or rift Found both on land and at the bottom of the ocean, where they are created by the process of seafloor spreading Many rift valleys are part of "triple junctions," a type of divergent boundary where three tectonic plates meet at about 120° angles Two arms of the triple junction can split to form an entire ocean The third, "failed rift" or aulacogen, may become a rift valley Example- Atlantic Ocean is a result of a triple junction that started in what is now the Gulf of Guinea on the west coast of Africa Rift valleys can also form at transform faults, where tectonic plates are grinding past each other (San Andreas Fault)
Explain why seafloor elevations are high at mid -ocean ridges and low farther away and what is the relationship between age and seafloor elevation?
Mid-ocean ridges are the newest or youngest crust and they spread out from the ridge in both directions as they are replaced so crust gets older as you move away from a mid-ocean ridge. Similarly, as the crust moves away it thickens and gets cooler as it gets denser it sinks lower into the asthenosphere decreasing the elevation.
List the two characteristics used to name igneous rocks. In terms of these two characteristics, list the combinations that define the following rock names: basalt, gabbro, rhyolite, granite
Mineralogy and grain size -Basalt: Fine grained, basaltic, mafic, minerals (pyroxene, calcium rich feldspar, calcium rich plagioclase) (45 to 80% oceanic crust) -Gabbro: cross- grained, basaltic, mafic, minerals (pyroxene, calcium rich feldspar, calcium rich plagioclase) (45 to 80% oceanic crust) -Rhyolite: fine grained, granitic, felsic, Minerals: (quartic, sodium rich feldspar, calcium rich plagioclase, feldspar) (25-45% continental crust)- Granite: Coarse-grained, granitic, felsic, Minerals: (quartic, sodium rich feldspar, calcium rich plagioclase, feldspar) (25-45% continental crust)
Where is most of the mass in the solar system found?
Most of the mass in the solar system is found in the Sun. (99.85%)
Describe the features and how it forms: volcanic island arc
On the other side of the trench, A volcanic arc is a chain of volcanoes, hundreds to thousands of miles long, that forms above a subduction zone on the other side of the trench across from the acretion wedge. An island volcanic arc forms in an ocean basin via ocean-ocean subduction. The Aleutian Islands off the coast of Alaska and the Lesser Antilles south of Puerto Rico are examples.
Identify the two most abundant elements that make up the continental crust
Oxygen (O) and Silicon (Si)
List the relative velocities of P-, S-, and surface waves
P-waves move at relatively 5-8 km/s. S-waves move at relatively 3.45-4.8 km/s. R waves move at relatively 3 km/s. Love waves move at relatively 2-6 km/s.
Explain the general three-phase origin for the Appalachian Mountains (you need not know the ages)
Phase 1: 3 tectonic plates all the oceanic crust between North America and a micro continent was subducted and the microcontinent was plastered to North America Phase 2: Ocean basin between Africa and modified North American crust continued to close and the volcanic rock from the island Arc became plastered on to North America Phase 3: Subduction continued and eventually Africa slammed into the edge of North America and this is what made the final stages of the Appalachians. Most significant in terms of crustal thickening and creating a large mountain belt. Refer to Plate Tectonic 3: 0:00-3:30
What is matter? Describe the three states (solid, liquid, gas) of matter (Box P.2)
Physical material that occupies space Solid- molecules remain in a fixed position and the shape does not alter Liquid- Molecules move relative to one another but remain touching so it can alter its shape to fill its container. Gas-molecules move freely- it can change shape, expand or contracts
Describe the various processes that drive motion of tectonic plates and control the rates of motion
Plate motion is controlled by forces applied along plate boundaries:- Ridge-push force: outward-directed push in a plate boundary caused by the gravitational potential energy of the elevated lithosphere at a mid-ocean ridge. (The higher lithosphere at mid-ocean ridges spreads sideways due to gravity and pushes the plates apart)- Slab-pull force: oceanic lithosphere mantle is cooler and denser than the warmer asthenosphere below, causing a subducted section to slowly pull the rest of the plate behind it. This is the more dominant force applied to plates. (as one plate subducts into the asthenosphere, the mass of the plate causes it to pull down and sink like an anchor) Control of motion:- Relative plate velocity: rate and direction of movement of a lithospheric plate with respect to another lithospheric plate. -Absolute plate velocity: movement of both plates are relative to a fixed reference point (in the mantle) that is not one of the plates Rate = distance / time
Describe the process of magnetic reversals and their relation to magnetic seafloor stripes (magnetic anomalies)
Plate tectonics and reversals of the Earth's magnetic field are responsible for the magnetic stripes found on the ocean floor. When magma flows out of a mid-ocean ridge, small, magnetic minerals in the magma align themselves to point in the direction of the Earth's current magnetic North. Over time, the Earth's magnetic field reverses its north-to-south polarity, and the magnetic minerals point in the opposite direction, creating a striped pattern.
Identify the general range of rates of relative plate motions - how fast do plates move?
Plates move about 1-15cm/year (same rate as fingernail growth)
Explain the physical characteristics of pumice and how it forms
Pumice is formed when volcanoes erupt explosively. It comes from the same kind of magma which would form granite or rhyolite, that is, a magma that contains lots of silica (quartz). Magma with lots of silica is usually thick and sticky -When magmas with intermediate (andesitic) or felsic (rhyolitic) compositions erupt explosively, they emit ash and the vesicular rock PUMICE. Pumice is usually lighter in color and less dense than scoria, and many pumice fragments have so many vesicles that they are light enough to float.
Explain what is meant by ""pyroclastic"" eruptions and materials"
Pyroclastic flow: a highly heated mixture, largely of ash and pumice fragments, traveling down the flanks of a volcano or along the surface of the ground driven by gravity. One of the most destructive forces of nature are pyroclastic flows, which consist of hot gases infused with incandescent ash and larger lava fragments. Also referred to as nuee ardentes (glowing avalanches), these fiery flows are capable go racing down steep volcanic slopes at speeds that can exceed 200 km (125 miles) per hour. Composed of two parts: a low-density cloud of hot expanding gases containing fine ash particles and a ground-hugging portion that contains most of the material in the flow. Move in a manner similar to snow avalanches .Pyroclastic material: the volcanic rock ejected during an eruption, including ash, bombs, and blocks.
Describe what is measured in calculating a magnitude using both the Richter and Moment magnitude scales.
Richter: The Richter scale defines quake magnitude- it is logarithmic, meaning that a one unit magnitude increase represents a 10 fold increase in maximum amplitude. Ex: Mag 7 earthquake is 10 times less than a mag 8 quake, and 1000 times greater than a mag 5 ---Measuring the size of earthquakes occurring using relatively high-frequency data from nearby seismograph stations As more seismograph stations were installed around the world, it became apparent that the method was valid only for certain frequency and distance ranges Moment mag scales: now used because it's more accurate- represents an earthquakes size, or moment magnitude. With this scale, scientists take into consideration the amplitude of several different waves, the dimensions of the slipped fault, and the displacement- it is also logorithmic ---Moment is a physical quantity proportional to the slip on the fault multiplied by the area of the fault surface that slips; it is related to the total energy released in the earthquake-Moment is then converted into a number similar to other earthquake magnitudes by a standard formula- The result is called the moment magnitude- The moment magnitude provides an estimate of earthquake size that is valid over the complete range of magnitudes, a characteristic that was lacking in other magnitude scales.
Describe the features and how it forms: accretionary wedges/prisms
Sediments accumulate and deform where oceanic and continental plates collide on the overriding plate. These sediments are scraped off the subducting plate lithosphere and appended to the edge of the continental crust.
Identify the types of material (solid, liquid, & gas) through which P-waves and S-waves may travel
Seismic waves abilities to travel through a certain material at a certain velocity depends on the density, rigidity, and compressibility of the material. This is known as "travel time" which is the amount of time a set of waves takes to travel from an epicenter to a seismometer.\ P waves travel slower in liquid (magma) than in solid (rock). S waves cannot travel through liquid
Identify the dominant control on the viscosity of a magma
Silica (Sio2) (temperature rise lowers viscosity but not as much)
Identify present-day examples that show each stage of divergent process
Stage 1- East African Rift- begining to slowly seperate Stage 2- Red Sea-- the Arabean sea and Africa were once linked, but are separating and forming a new sea, The Red Sea. Stage 3- Atlantic Ocean-- vast ocean that exists today came from divergent spreading
Explain what kinds of eruptions and how some eruptions can cause climate change. How long do these temperature changes last?
The gases and dust particles thrown into the atmosphere during volcanic eruptions have influences on climate. Most of the particles spewed from volcanoes cool the planet by shading incoming solar radiation. The cooling effect can last for months to years depending on the characteristics of the eruption.
The solar system began as a nebula. Describe the characteristics of a nebula.
The nebular theory is that stars formed within collapsing patches of a nebula. As nebulae become so dense, they began collapsing due to the inward pull of gravity. Compression of material into smaller volume causes its temperature to rise (the more dense, the more hot). The swirling motion becomes organized around an axis so that the collapsing nebula take the shape of a flattened disk, known as an acretion disk. When it becomes hot enough, it begins to excrete light and the central ball becomes a protostar. If everything goes right for the protostar and fusion takes place to form a hydrogen nuclei, then crazy amounts of energy and light would be produced, making it a star.
Describe the stages of evolution of divergent boundaries from continental rifting to seafloor spreading
The process of stretching and breaking a continent apart is called rifting. Stage 1-Thinning and stretching of continental crust-Thinned continental crust makes continental shelves. Mid ocean ridge forms and an abyssal plain. Stage 2-Continental crust ruptures and separates-New oceanic crust is made and fills in the gap as two continents move apart-Low lying regions of linear sea-Continent no longer stretching but moving apart. -- Hot asthenosphere rises beneath the ridge and begins to melt- magma rises and accumulates in a magma chamber (it can solidify into Gabrro on the sides, or rise higher and solidify in wall cracks called dikes, or seep out of the seafloor as lava. All of this represents new oceanic crust) Stage 3-Ocean basin widens-Steady-state seafloor spreading and oceanic crust formation. ---This continues on and on, and the stretching force or tension applied to new crust causes it to break, resulting in faults along the ridge axis, which can cause divergent earthquakes if there is slip.
Describe the silica tetrahedron
The silica tetrahedron's chemical formula is (SiO4)4-. It is a centered silicon atom surrounded by four oxygen atoms. This makes a geometric figure with 4 equilateral triangles which makes the tetrahedron
Why did the spin rate of the solar nebula increase? What important effect did this have on the shape of the nebula?
The spin rate of the solar nebula increased because the gas moved inward causing it to become denser Think of a spinning ice skater pulling their arms or legs inward (Figure 1.8.) This caused it to form a disk like shape with a bulbous center
Describe the relative motion between plates at transform boundaries
The two plates are going to be parallel and sliding horizontally past one another
Explain how an earthquake may generate tsunamis and describe the changes in Tsunami waves as they move from deeper to shallower water.
The uplift of the sea floor, or upward motion of a plate pushes water upward, causing waves in both directions that build energy. Friction between the base of the wave and the seafloor slows the bottom of the wave, causing the back of the wave to catch up with the front and build the wave higher, making tsunamis much bigger as they get to shallower water.
Explain the relationship between the viscosity and SiO2 (silica) content for felsic and mafic magmas
The viscosity of magma is directly related to its silica content--the more silica in magma, the greater its viscosity. Silica impedes the flow of magma because silicate structures start to link together into long chains early in crystallization process. Rhyolitic (felsic) lava, with its high silica content (over 70 percent), is very viscous and forms short, thick flows. Basaltic (mafic) lava, with a lower silica content (about 50 percent), is more fluid and may travel a long distance (90 miles/150 km) before congealing.
Describe the temperature gradient in the accretion disk around the sun. How did this gradient influence the distribution of planet types (i.e., why are inner planets dominantly rocky material and the outer planets dominantly frozen gases?)
There is a frost line between the terrestrial and jovial planets. The terrestrial planets are close enough to the sun so that condensation cannot happen, but the jovial planets are too far away, so it is cold enough for condensation to occur.
What is the estimated age for formation of the earth and solar system and where does this age come from?
This age comes from when an accretion disk developed within a nebula in an arm of the Milky way Galaxy. The central ball of this disk collapsed to become the sun around 4.57 Ga. The growth of the Earth to nearly its present size, and its differentiation, occurred between 4.56 Ga and 4.54 Ga. (When the earth was formed, the universe was already over 9 billion years old)
Calculate the Richter magnitude of an earthquake using a seismogram
To calculate this, you must measure the amplitude of the largest wave, then calculate the difference between s and p wave arrival to determine distance to epicenter. Then you'd draw a line from these two results to find the mag.
Describe and explain the formation of the features that define vesicular rocks such as pumice, and scoria
Vesicular rocks contain holes (vesicles) where gas bubbles were present in magma. Scoria forms from basaltic magmas, while pumice forms from rhyolitic magmas - which usually contain more gas. Pumice has a much higher concentration of trapped bubbles - so many that the walls between them are very thin. The vesicles in pumice contain enough air that the rock will float on water
List the two main controls on the explosiveness of volcanic eruptions and explain how they influence the eruptive style
Viscosity (the silica content) and amount of dissolved gas. Viscosity: resistance of flow of the material More viscous more eruptive Dissolved gas: viscosity controls how this gas will act and that in turn controls whether we get an explosive eruption or a relatively low viscosity lava flow. In summary, to get an explosive eruption, gas bubbles in magma not being able to expand, not being able to rise, stuck in magma, pressure is building, reaching a point where pressure is so great that it is greater than the resisting force of the viscosity and the bubbles instantaneously expand and shoot this material very violently.
Describe volcanic ash and explain how it forms; describe the differences between volcanic ash and cinders/lapilli, and volcanic bombs
Volcanic ash: "instant" quenching sometimes occurs during violent volcanic eruptions that produce tiny shards of glass called volcanic ash. Cinder cone/lapilli: a rather small volcano built primarily of pyroclastics ejected from a single vent. They usually harden before they hit the ground. ---Marble, golf sized pieces forms from fragmented rock or clotted ash or clotted lava (called cinders). Volcanic bomb: Blocks that were still soft during eruption, so they become streamlined as they fall, or flatten like pancakes on impact.
Explain Alfred Wegener's hypothesis of continental drift and what was lacking (or wrong) from his hypothesis, which led to lack of acceptance of this idea
Wegner hypothesized the idea of Pangea super continent in the 1930s. He attempted to prove this with "glacial striations" (scratches carved against glaciers) in non polar latitudes, showing evidence of "paleozoic continental glaciers," that were once connected. He also looked at evidence of animal migration that could not have taken place without land locked places. He also found specific rocks on different continents. His nay sayers had "fixist views" but now a "mobilist view" is used to confirm plate tectonics.
Describe the features and how it forms: continental volcanic arcs
a continental volcanic arc forms along the margin of a continent where oceanic crust subducts beneath continental crust. The Cascade Volcanoes are an example. In both cases, the volcanic arc is an active landform.
Describe the characteristics of mineralogy and SiO2 content that are used to distinguish felsic rocks from mafic rocks
felsic and mafic are two types of the 4 major types of melt. This is based on how much silica, iron, magnesium oxide and other oxide compounds are involved. Felsic contains the most feldspar and silica (si02), lowest temp, highest viscosity- lightly colored with black flecks-(Light colors= non-ferromagnesium minerals) Mafic: -Mafic: contains a lot of minerals with magnesium and iron (Ma and Fe), low silica, dark colored (green, black etc)
Describe the features and how it forms: ocean trenches
steep depressions in the deepest parts of the ocean, where an old oceanic crust from one tectonic plate is pushed beneath another plate, raising mountains, causing earthquakes, and forming volcanoes on the seafloor and on land. Trenches are formed by subduction.
Explain how calderas form
the magma chamber empties, the volcano collapses, a caldera forms (a large basin-shaped crater at the top of a volcano)
Describe the geometry of transform boundaries that link segments of mid-ocean ridges
zig-zag pattern of mid-ocean ridges reflect the spreading segments with transform faults (two slabs of rock moving away from the ridge against each other)- The overall shape of the ridge mimics the edge of Africa and South America split- Opposite sides of fracture zones have different elevations because they are formed by seafloor spreading at different times and different amounts of time to cool and subside- Younger parts are warmer and higher than older parts
