Earth Science Final

Uniformitarianism

states that the physical, chemical, and biological laws that operate today have also operated in the geologic past

Megathrust Fault

the plate boundary between a subducting slab of oceanic lithosphere and an overlying continental plate; the sites of earth's largest earthquakes

Elastic rebound

the sudden release of stored strain in rocks that results in movement along a fault

Explosive eruptions

typical of andesitic-to-rhyolitic magmas which have high viscosities and high gas contents

Nonexplosive eruptions

typical of basaltic-to-andesitic magmas which have low viscosities and low gas contents

Divergent Boundary

-A ____ occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth's mantle to the surface, solidifying to create new oceanic crust. -Opposite of a ___ boundary, a ____ boundary is formed by the spreading of a tectonic plate. This process feeds magma to the surface, creating new crust. -___ zones in oceanic plates form a geological feature called a ridge, forced upward by the pressure of the rising magma. -When ___ boundaries occur in continental plates, a different geological feature, called a rift valley, is formed. These depressions slowly fill with water, forming lakes, as their level drops. Ultimately, they will form the floor of a new ocean.

Strike-slip fault

-A fault in which the dominant displacement is horizontal and parallel to the strike (the compass direction) of the fault surface is called a strike-slip fault -Recall that some strike-slip faults, called transform faults, cut through the lithosphere and accommodate motion between two large tectonic plates. Numerous transform faults cut the oceanic lithosphere and link segments of oceanic ridges

wave-cut platform

-A relatively flat, bench-like surface, called a wave-cut platform, is left behind by the receding cliff. -The platform broadens as wave attack continues.

Active continental margins

Active continental margins are located along convergent plate boundaries where oceanic lithosphere is being subducted beneath the leading edge of a continent. Deep-ocean trenches are the major topographic expression at convergent plate boundaries.

Strike-slip fault

Faults in which the dominant displacement is horizontal and parallel to the direction of the fault trace are called strike-slip faults.

continental slope

Marking the seaward edge of the continental shelf is the continental slope, a relatively steep feature that marks the boundary between continental crust and oceanic crust.

Plates

Massive rocks that make up the outer layer of the Earth's surface and whose movement along faults triggers earthquakes

continental rise

The continental slope merges into a more gradual incline known as the continental rise that may extend seaward for hundreds of kilometers. The continental rise consists of a thick accumulation of sediment that has moved down the continental slope and onto deep-ocean floor.

Absolute Dating

Unlike relative dating methods, absolute dating methods provide chronological estimates of the age of certain geological materials associated with fossils, and even direct age measurements of the fossil material itself.

Fault scarps

Vertical displacements along dip-slip faults may produce long, low cliffs called fault scarps. Fault scarps are produced by displacements that generate earthquakes.

Seismic waves

Waves that transmit the energy released by an earthquake

Catastrophism

belief that Earth's landscapes were formed by great catastrophes

Tsunami

-A tsunami is a series of extremely long waves caused by a large and sudden displacement of the ocean, usually the result of an earthquake below or near the ocean floor. -This force creates waves that radiate outward in all directions away from their source, sometimes crossing entire ocean basins. -Tsunami are waves caused by sudden movement of the ocean surface due to earthquakes, landslides on the sea floor, land slumping into the ocean, large volcanic eruptions or meteorite impact in the ocean.

Active continental margins

-An active continental margin is a coastal region that is characterized by mountain-building activity including earthquakes, volcanic activity, and tectonic motion resulting from movement of tectonic plates. -Characteristics of active continental margins include: Found on mostly convergent plate boundaries, Continental slope descends abruptly into a deep-ocean trench (no continental rise), Located primarily around the Pacific Ocean -Active margins typically have a narrower and steeper continental shelf and slope. They can also be subsiding or uplifting. -Active continental margins are also associated with subduction zones, often include a deep offshore trench.

Faults

-An earthquake is ground shaking caused by the sudden and rapid movement of one block of rock slipping past another along fractures in Earth's crust, called faults. -Most faults are locked, except for brief, abrupt movements when sudden slippage produces an earthquake. -Faults are locked because the confining pressure exerted by the overlying crust is enormous, causing these fractures in the crust to be "squeezed shut."

Temperature (seawater density)

-An increase in temperature, on the other hand, causes water to expand and results in a decrease in seawater density. -Temperature has the greatest influence on surface seawater density because variations in surface seawater temperature are greater than salinity variations. Cold water that also has high salinity is some of the highest-density water in the world. -Density increases rapidly with depth because the water temperature is getting colder. -Except for some shallow inland seas with a high rate of evaporation, the highest density water is found at the greatest ocean depths.

Cinder Cones

-As the name suggests, cinder cones (also called scoria cones) are built from ejected lava fragments that begin to harden in flight to produce the vesicular rock scoria -Because cinder cones are composed of loose fragments rather than solid rock, the lava usually flows out from the unconsolidated base of the cone rather than from the crater. Most cinder cones are produced by a single, short-lived eruptive event -Ex: Cerro Negro, a cinder cone in Nicaragua, Parícutin, a cinder cone located in Mexico

Convergent Boundary

-At a convergent plate boundary, tectonic plates move toward one another and collide -Oftentimes, this collision forces the denser plate edge to subduct, or sink beneath the plate edge that is less dense -These subduction zones can create deep trenches

sea arch

-At first, sea caves may form. When two caves on opposite sides of a headland unite, a sea arch results -Eventually, the arch falls in, leaving an isolated remnant, or sea stack, on the wave-cut platform.

wave-cut platform

-At the base of most cliffs along a rocky coast one finds a flat surface at about the mid-tide elevation. -This is a bench-like feature called a wave-cut platform, or wave-cut bench. -Wave-cut platforms are formed by wave action on the bedrock along the coast. The formation process can take a long time, depending on the type of rock present. wave-cut platforms may be incomplete, with erosional remnants on the horizontal wave-cut surface. -These remnants are called sea stacks, and they provide a spectacular type of coastal landform. Some are many meters high and form isolated pinnacles on the otherwise smooth wave-cut surface. -Because erosion is a continual process, these features are not permanent

Cinder cones

-Cinder cones = steep-sided structures composed mainly of pyroclastic debris, typically having a basaltic composition -Lava flows sometimes emerge from the base of a cinder cone but typically do not flow out of the crater -Are small relative to other major types of volcanoes, reflecting the fact that they form quickly as single eruptive events -Easily succumb to weathering and erosion -Symmetrical -Steep-sided -Loose accumulations of ejected scoria -Commonly pea to walnut-sized fragments -Basaltic composition, reddish-brown color -Some produce lava flows -Craters are relatively large and deep

Composite volcanoes

-Composite volcanoes = aka stratovolcanoes -Located around the Ring of Fire -Large, symmetrical cones -Built by layers of cinder and ash alternating with lava flows -Primarily silica-rich andesitic magma -Associated with explosive eruptions and abundant pyroclastic material -Steep summit and gradually sloping flanks -Ex: Mt. St. Helens, Mount Rainier & other volcanoes of the Cascade Range in the NW USA

Normal Faults

-Dip-slip faults are classified as normal faults when the hanging wall block moves down relative to the foot-wall block. Because of the downward motion of the hanging wall block, normal faults accommodate stretching, or extension, of the crust. -Normal faults are found in a variety of sizes. Some are small, having displacements of only 1 meter, while others extend for tens of kilometers and may sinuously trace the boundary of a mountain front. Most large normal faults have relatively steep dips that tend to flatten out with depth. -In the western United States, large normal faults are associated with structures called fault-block mountains.

Reverse Fault

-Dip-slip faults in which the hanging wall block moves up relative to the footwall block are called reverse faults. Whereas normal faults occur in tensional environments, reverse faults result from strong compressional stresses. -A common type of reverse fault, called a thrust fault, has a low angle of dip (less than 45 degrees), which allows the overlying block to slide over the top of the underlying block.

Catastrophism

-During the 1600s and 1700s, the doctrine of catastrophism strongly influenced people's thinking about Earth. Briefly stated, catastrophists believed that Earth's varied landscapes had been fashioned primarily by great catastrophes. -This philosophy was an attempt to fit the rate of Earth's processes to the prevailing ideas about Earth's age.

Composite Volcanoes

-Earth's most picturesque yet potentially dangerous volcanoes are composite volcanoes, also known as stratovolcanoes. Most are located in a relatively narrow zone that rims the Pacific Ocean, appropriately called the Ring of Fire -Classic composite cones are large, nearly symmetrical structures consisting of alternating layers of explosively erupted cinders and ash interbedded with lava flows. -Ex: Mount Mayon in the Philippines and Fujiyama in Japan. Mt. St. Helens

Hypocenter

-Earthquakes tend to occur along preexisting faults where internal stresses cause the crustal rocks to rupture or break into two or more units. -The location where slippage begins is called the hypocenter, or focus. -Earthquake waves initially radiate out from this spot into the surrounding rock.

Convergent/Transform Plate Boundaries

-Faults associated with convergent and transform plate boundaries are the source of most large earthquakes. -Earth's strongest earthquakes most often occur along large faults associated with convergent plate boundaries.

Dip-slip Faults

-Faults in which movement is primarily parallel to the dip (or inclination) of the fault surface are called dip-slip faults. -It has become common practice to call the rock surface that is immediately above the fault the hanging wall block and to call the rock surface below the footwall block

Hard Stabilization

-Hard stabilization structures, such as groins, are built at right angles to the shore to prevent the movement of sand down the coast and maintain the beach, while other hard stabilization structures, such as breakwaters and seawalls, are built parallel to the beach to protect the coast from the force of waves. -These structures are built to stay in place for years, but they are not always the desired solution because they take away from the aesthetic beauty of the beach. -They also interfere with the natural ecosystem, threatening habitats and nesting grounds of native shoreline species.

marine terrace

-If a wave-cut platform is uplifted above sea level by tectonic forces, it becomes a marine terrace. -They are recognized by their gentle seaward-sloping shape and are often perceived as desirable sites for coastal development.

Principle of Inclusions

-Inclusions are fragments of one rock unit that have been enclosed within another. -The principle of inclusions says that the rock mass adjacent to the one containing the inclusions must have been there first in order to provide the rock fragments. Therefore, the rock mass that contains the inclusions is the younger of the two.

Lava Composition and Viscosity

-Mafic magmas are low in silica and contain more dark, magnesium- and iron-rich mafic minerals, such as olivine and pyroxene. -Felsic magmas are higher in silica and contain lighter colored minerals such as quartz and orthoclase feldspar. The higher the amount of silica in the magma, the higher is its viscosity. -Viscosity determines what the magma will do. Mafic magma is not viscous and will flow easily to the surface. Felsic magma is viscous and does not flow easily

Where and how do tsunamis form?

-Major undersea earthquakes often set in motion a series of large ocean waves that are known by the Japanese name tsunami ("harbor wave"). -Most tsunamis are generated by displacement along a megathrust fault that suddenly lifts a large slab of seafloor. -Tsunamis cause major destruction in coastal areas if they strike the shoreline.

Formation of a tsunami

-Megathrust displacement lifts large slabs of seafloor, displaces water, and generates a tsunami -Low amplitude wave travels at very high speed in open ocean -Amplitude can reach tens of meters in shallow coastal waters -Arrival on shore is preceded by a rapid withdrawal of water from beaches, followed by what appears as a rapid rise in sea level with a turbulent surface

Decompression Melting

-Melting that occurs as rock ascends due to a drop in confining pressure -takes place within Earth when a body of rock is held at approximately the same temperature but the pressure is reduced

Decompression Melting

-Melting, which is accompanied by an increase in volume, occurs at progressively higher temperatures with increased depth. This is the result of the steady increase in confining pressure exerted by the weight of overlying rocks. Conversely, reducing confining pressure lowers a rock's melting temperature. -When confining pressure drops sufficiently, decompression melting is triggered. Decompression melting occurs wherever hot, solid mantle rock ascends, thereby moving into regions of lower pressure. The process of decompression melting is responsible for generating magma along divergent plate boundaries (oceanic ridges) where plates are rifting apart. -Decompression melting also occurs when ascending mantle plumes reach the uppermost mantle

breakwater

-One such structure is a ___, which is designed to protect boats from the force of large breaking waves by creating a quiet-water zone near the shore. However, the reduced wave activity along the shore behind the __ may allow sand to accumulate. -When this happens, cities can use a dredge to remove sand from the protected quiet- water zone and deposit it farther downstream, where longshore currents continue to move the sand down the coast

Active continental margins

-usually narrow and consists of highly deformed sediments -Such margins occur where oceanic lithosphere is being subducted beneath the margin of a continent

Partial Melting

-Partial melting is what happens when only some parts of a rock melt; it takes place because rocks are not pure materials. -Most rocks are made up of several minerals, each of which has a different melting temperature.

Passive continental margins

-Passive continental margins are geologically inactive regions located some distance from plate boundaries. As a result, they are not associated with strong earthquakes or volcanic activity -Passive continental margins develop when continental blocks rift apart and are separated by continued seafloor spreading. As a result, the continental blocks are firmly attached to the adjacent oceanic crust.

Passive continental margins

-Passive continental margins occur where the transition between oceanic and continental crust which is not an active plate boundary. -Passive margins are characterized by wide beaches, barrier islands, broad coastal plains. -Offshore passive margins typically have a wider and flatter continental shelf and slope.

Density of seawater

-Salinity, temperature and depth all affect the density of seawater. -Density is a measure of how tightly a certain amount of matter is packed into a given volume.

Methods scientists use to study Earth's interior

-Scientists use information from seismic waves to understand what makes up the Earth's interior. The properties of seismic waves allow scientists to understand the composition of Earth's interior. -One ingenious way scientists learn about Earth's interior is by looking at earthquake waves. Seismic waves travel outward in all directions from where the ground breaks and are picked up by seismographs around the world. -Two types of seismic waves are most useful for learning about Earth's interior. (S and P waves)

Studying Earth's Interior

-Seismic waves are the only way to "see" inside the interior -Waves are reflected at boundaries -Refracted through layers -Diffracted around obstacles -Velocity increases with depth as stiffness and compressibility of rock change - Can be used to interpret composition and temperature of rock

Shield Volcanoes

-Shield volcanoes are produced by the accumulation of fluid basaltic lavas. This type of volcano is a broad, slightly domed structure that resembles a warrior's shield -Most shield volcanoes begin on the ocean floor as seamounts (submarine volcanoes), a few of which grow large enough to form volcanic islands. Ex: the Hawaiian Islands, the Canary Islands, Iceland, the Galápagos Islands, and Easter Island; and (continental crust) Nyamuragira, Africa's most active volcano, and Newberry Volcano, Oregon. -Mauna Loa, Earth's largest volcano, is one of five shield volcanoes that collectively make up the Big Island of Hawaii. Shield volcanoes are built primarily of fluid basaltic lava flows and contain only a small percentage of pyroclastic materials. -Kilauea Volcano, one of the most active and intensely studied shield volcanoes in the world

Shield volcanoes

-Shield volcanoes consist of many successive lava flows of low-viscosity basaltic lava but lack significant amounts of pyroclastic debris. -Lava tubes help transport lava far from the main vent, resulting in very gentle, shield-like profiles -Most begin as seamounts that grow from Earth's seafloor -Ex: Mauna Loa, Mauna Kea, Kilauea

Principle of Superposition

-Steno applied a very simple rule that has come to be the most basic principle of relative dating— the principle of superposition. The principle simply states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below. -This rule also applies to other surface- deposited materials, such as lava flows and beds of ash from volcanic eruptions.

Hard Stabilization

-Structures built to protect a coast from erosion or to prevent the movement of sand along a beach are known as hard stabilization. -Protective structures divert the ocean's energy temporarily from private properties but usually refocus that energy on the adjacent beaches. Many structures interrupt the natural sand flow in coastal currents, robbing affected beaches of vital sand replacement.

Lava Domes

-created by small masses of lava which are too viscous (thick) to flow very far. -The magma from volcanic domes just pile up over and around the vent. -Lava domes can explode violently, releasing a huge amount of hot rock and ash.

continental shelf

-The continental shelf is a gently sloping, submerged surface extending from the shoreline toward the deep-ocean basin. It consists mainly of continental crust capped with sedimentary -The continental shelf tends to be relatively featureless; however, some areas are mantled by extensive glacial deposits and thus are quite rugged. In addition, some continental shelves are dissected by large valleys running from the coastline into deeper waters. -Although continental shelves represent only 7.5 percent of the total ocean area, they have economic and political significance because they contain important reservoirs of oil and natural gas, and they support important fishing grounds.

Methods scientists use to study Earth's interior

-The detailed studies of seismic waves described above help scientists locate and measure earthquakes. Knowing how seismic waves behave has also given us a better understanding of the nature of Earth's interior. -The best way to learn about Earth's interior is to dig or drill a hole and examine it directly. Unfortunately, this is possible only at shallow depth -Using the waves recorded on seismograms to visualize Earth's interior structure is challenging. -Seismic waves do not travel along straight paths; instead, they are reflected, refracted, and diffracted as they pass through our planet. They reflect off boundaries between different layers; they refract (change direction) when passing from one layer to another layer; and they diffract (follow a curved path) around obstacles they encounter

Partial Melting

-The incomplete melting of rocks is known as partial melting, a process that produces most magma. -Partial melting can be likened to a chocolate chip cookie set out in the Sun. The chocolate chips represent the minerals with the lowest melting points because they begin to melt before the other ingredients -When rock partially melts, the molten material melts and separates from the surrounding solid components. So, because molten rock is less dense than the surrounding solids, it rises toward Earth's surface.

Lava Composition and Viscosity

-The more silica in magma, the greater its viscosity. Silicate structures begin to link together into long chains early in the crystallization process, which makes the magma more rigid and impedes its flow. Consequently, silica-rich rhyolitic lavas are the most viscous and tend to form comparatively short, thick flows. -By contrast, basaltic lavas, which contain much less silica, are relatively fluid and have been known to travel 150 kilometers (90 miles) or more before solidifying. -The vast majority of Earth's lava, more than 90 percent of the total volume, is estimated to be basaltic (mafic) in composition -Andesitic lavas account for most of the rest, while rhyolitic (felsic) flows make up as little as 1 percent of the total. (Rhyolitic magmas tend to extrude mostly volcanic ash rather than lava.) -On land, hot basaltic lavas, which are usually very fluid, generally flow in thin, broad sheets or stream- like ribbons. -Silica-rich, rhyolitic lava, by contrast, often moves too slowly to be perceived. Furthermore, most rhyolitic lavas seldom travel more than a few kilometers from their vents. -As you might expect, andesitic lavas, which are intermediate in composition, exhibit flow characteristics between these extremes.

sea cliffs

-The most widespread landforms of erosional coasts are sea cliffs. These very steep to vertical bedrock cliffs range from only a few meters high to hundreds of meters above sea level. -The vertical nature of sea cliffs is the result of wave-induced erosion near sea level and the subsequent collapse of rocks at higher elevation.

Gas Content (eruption)

-The nature of volcanic eruptions also depends on the amount of dissolved gases held in the magma body by the pressure exerted by the overlying rock. -This is analogous to how carbon dioxide is retained in cans and bottles of soft drinks. When the pressure is reduced on a soft drink by opening the cap, the carbon dioxide begins to bubble out of solution. Likewise, the gases dissolved in magma tend to come out of solution when the confining pressure is reduced. The most abundant gas found in most magma is water vapor.

Megathrust Fault

-The plate boundary between a subducting slab of oceanic lithosphere and an overlying continental plate form a fault termed a megathrust fault. -Megathrust faults have produced the majority of Earth's most powerful and destructive earthquakes

Principle of Cross-cutting Relationships

-The principle of cross-cutting relationships states that geologic features that cut across rocks must form after the rocks they cut through. -Ex: faults and igneous intrusions

Principle of Lateral Continuity

-The principle of lateral continuity refers to the fact that sedimentary beds originate as continuous layers that extend in all directions until they eventually grade into a different type of sediment or until they thin out at the edge of the basin of deposition -Although rock outcrops may be separated by a considerable distance, the principle of lateral continuity tells us that they once formed a continuous layer. This principle allows geologists to relate rocks in isolated outcrops to one another.

wave-cut cliffs

-wave-cut cliffs originate in the cutting action of the surf against the base of coastal land. -As erosion progresses, rocks overhanging the notch at the base of the cliff crumble into the surf, and the cliff retreats

Partial melting

-The process by which most igneous rocks melt -Since individual minerals have different melting points, most igneous rocks melt over a temp. range of a few hundred degrees -If the liquid is squeezed out after melting has occurred, a melt with a higher silica content results

Parts of an earthquake

-The surface where they slip is called the fault or fault plane. -The location below the earth's surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.

Half-life

-The time required for one-half of the nuclei in a sample to decay is called the half-life of the isotope. Half-life is a common way of expressing the rate of radioactive disintegration. -If the half-life of a radioactive isotope is known and the parent-daughter ratio can be determined, the age of the sample can be calculated. -When the quantities of parent and daughter are equal (ratio 1:1), we know that one half-life has transpired. When one-quarter of the original parent atoms remain and three-quarters have decayed to the daughter product, the parent-daughter ratio is 1:3, and we know that two half-lives have passed. After three half-lives, the ratio of parent atoms to daughter atoms is 1:7 (one parent atom for every seven daughter atoms) -half life 1, parent ½, daughter ½; half life 2, parent ¼, daughter ¾

Viscosity (eruption)

-The viscosity of the magma, however, is also an important factor in determining whether an eruption will be explosive or nonexplosive. -A low-viscosity magma, like basalt, will allow the escaping gases to migrate rapidly through the magma and escape to the surface. -However, if the magma is viscous, like rhyolite, its high polymerization will impede the upward mobility of the gas bubbles.

Shield Volcanoes

-These are large, broad volcanoes that look like shields from above - hence the name. -The lava that pours out of shield volcanoes is thin, so it can travel for great distances down the shallow slopes of the volcano. -These volcanoes build up slowly over time, with hundreds of eruptions, creating many layers. -Ex: Mauna Loa and Mauna Kea.

Cinder cone

-These are the simplest type of volcano. -They occur when particles and blobs of lava are ejected from a volcanic vent. -The lava is blown violently into the air, and the pieces rain down around the vent.

Half-life

-Time required for one half of the nuclei in a sample to decay -One half-life has transpired when quantities of parent and daughter are equal (1:1 ratio)

groin

-To maintain or widen beaches that are losing sand, __ are sometimes constructed. A __ is a barrier built at a right angle to the beach to trap sand that is moving parallel to the shore. -__ can cause the longshore current beyond them to become sand-starved. As a result, the current erodes sand from the beach on the downstream side of the __. -Because it has been shown that __ often do not provide a satisfactory solution, using them is no longer the preferred method of keeping beach erosion in check.

Features Formed at Convergent Boundaries

-Trenches are geological features formed by convergent boundaries. -When two tectonic plates converge, the heavier plate is forced downward, creating a subduction zone. This process results in the formation of a trench. -When two continental plates converge, neither of the buoyant plates is able to give way and subduct beneath the other. This results in a powerful collision that produces tremendous, crushing pressure. Ultimately, this pressure causes large vertical and horizontal displacements, forming towering mountain ranges. -Another geological feature that results from a subduction zone is volcanoes. When the plate being forced downward begins to melt, this magma rises to the surface, forming volcanoes.

Transform Boundary

-Two plates sliding past each other forms a __ plate boundary. -Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon. Earthquakes are common along these faults. -In contrast to convergent and divergent boundaries, crust is cracked and broken at ___ margins, but is not created or destroyed. -A __ boundary connects two diverging boundaries, creating a fault line. This line represents an area of shear, where two plates are moving horizontally against one another.

Formation of Tsunamis

-Undersea earthquakes, which typically occur at boundaries between Earth's tectonic plates, cause the water above to be moved up or down. Tsunami waves are formed as the displaced water, which acts under the influence of gravity, attempts to find a stable position again. -Undersea landslides, which can be caused by large earthquakes, can also cause tsunami waves to form as water attempts to find a stable position. -Undersea volcano eruptions can create enough force to uplift the water column and generate a tsunami. -Asteroid impacts disturb the water from above, as momentum from falling debris is transferred to the water into which the debris falls.

Normal fault

A fault in which the rock above the fault plane has moved down relative to the rock below

Viscosity (eruption)

-Viscosity (viscous = sticky) is a measure of a fluid's mobility. The more viscous a material, the greater is its resistance to flow. -Magma's viscosity depends primarily on its temperature and silica content: The more silica in magma, the greater its viscosity. Silicate structures begin to link together into long chains early in the crystallization process, which makes the magma more rigid and impedes its flow -The effect of temperature on magma viscosity can be compared to the effect of temperature on pancake syrup. Just as heating syrup makes it more fluid (less viscous), temperature also strongly influences the viscosity and mobility of lava. As lava cools and begins to congeal, its viscosity increases, and the flow eventually halts.

Lava Composition and Viscosity

-Viscosity of magma is controlled by temperature, silica content, and dissolved gasses -Decrease temperature = increased viscosity -Increased silica = increased viscosity -Decrease dissolved gas = increased viscosity

Factors to determine explosiveness of volcanoes

-Volcanic eruptions exhibit a range of behavior from quiescent (nonexplosive) eruptions that produce outpourings of fluid lava (geologists often refer to these as effusive eruptions) to explosive eruptions -The two primary factors that determine how magma erupts are its viscosity and gas content.

Decompression Melting

-When tectonic plates under the Earth's surface shift, they create space between them. Hot rock under these plates then rises to occupy the space. -As the rock rises, the pressure placed on the rock decreases and causes the rock to melt. -This occurs at Mid-Ocean Ridges

Impacts of Human Generated CO2

-When the carbon dioxide concentration goes up, temperature goes up, and vice versa. -increased levels of carbon dioxide and other greenhouse gases in the atmosphere can amplify the natural greenhouse effect, causing the temperature of the Earth's atmosphere, ocean, and land surface to increase.

Convergent Boundary

-When two plates come together, it is known as a ___ boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into mountain ranges or one of the plates may bend down into a deep seafloor trench. -A chain of volcanoes often forms parallel to ___ plate boundaries and powerful earthquakes are common along these boundaries. -At ___ plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at ___ boundaries, continental crust is created and oceanic crust is destroyed. -

Seismic Waves

-Where seismic waves speed up or slow down, they refract, changing the direction in which they are traveling. Where seismic waves encounter an abrupt boundary between two very different layers, some of the seismic wave energy is reflected, bouncing back at the same angle it struck. -The reflections and refractions of seismic waves allow the layers and boundaries within the earth to be located and studied. -By tracking seismic waves, scientists have learned what makes up the planet's interior . -P-waves slow down at the mantle core boundary, so we know the outer core is less rigid than the mantle. -S-waves disappear at the mantle core boundary, so the outer core is liquid.

seawall

-a __, which is designed to armor the coast and defend property from the force of breaking waves. ___ reflect the force of unspent waves seaward. -As a consequence, the beach to the seaward side of the __ experiences significant erosion and may, in some instances, be eliminated entirely

Effects of Human Generated CO2

-a change in the atmosphere's CO2 content could influence air temperature. -Most of the observed increase in global average temperatures since the mid-twentieth century is extremely likely due to the observed increase in human-generated greenhouse gas concentrations -One important impact of human-induced global warming is a rise in sea level. -Potential weather changes include shifts in the paths of large-scale storms, which in turn would affect the distribution of precipitation and the occurrence of severe weather. -Other possibilities include stronger tropical storms and increases in the frequency and intensity of heat waves and droughts.

Seismic Waves

-a form of energy that travels through the lithosphere & earth's interior -radiate out from the focus (hypocenter), the location where slippage begins

oblique-slip fault

-a special type fault that forms when movement is not exactly parallel with the fault plane. -Oblique movement occurs when normal or reverse faults have some strike-slip movement and when strike-slip faults have either some normal or reverse movement.

Composite volcanoes

-aka stratovolcanoes make up some of the world's most memorable mountains. -These volcanoes have a conduit system inside them that channels magma from deep within the Earth to the surface. -Ex: Mount Rainier, Mount Fuji, and Mount Cotopaxi, Mount St. Helens

Passive continental margins

-geologically inactive regions located some distance from plate boundaries -Develop when continental blocks rift apart and are separated by continued seafloor spreading -As a result, the continental blocks are firmly attached to the adjacent oceanic crust

Uniformitarianism

-pillar of geology today: uniformitarianism. It simply states that the physical, chemical, and biological laws that operate today have also operated in the geologic past. -This means that the forces and processes that we observe presently shaping our planet have been at work for a very long time.

Principle of Original Horizontality

-the principle of original horizontality. It simply states that layers of sediment are generally deposited in a horizontal position. -Thus, if we observe rock layers that are flat, we know that they have not been disturbed and still have their original horizontality. But if layers are folded or inclined at a steep angle, they must have been moved into that position by crustal disturbances sometime after their deposition

sea arch

-the sea arch, which forms as the result of different rates of erosion typically due to the varied resistance of bedrock -It is common for sea arches to form when a rocky coast undergoes erosion and a wave-cut platform develops. -Continued erosion can result in the collapse of an arch, leaving an isolated sea stack on the platform.

Transform Faults

-transform plate boundaries or simply transform faults accommodate motion between two tectonic plates. -Most large transform faults are not perfectly straight or continuous; instead, they consist of numerous branches and smaller fractures that display kinks and offsets. Earthquakes can occur along any of these branches.

Transform Boundary

-where plates slide past 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

Divergent Boundary

-where two plates are moving apart -can form within continents but will eventually open up and become ocean basins -On land: Divergent boundaries within continents initially produce rifts, which produce rift valleys -Under the sea: The most active divergent plate boundaries are between oceanic plates and are often called mid-oceanic ridges.

Absolutism

A form of government in which the ruler is an absolute dictator (not restricted by a constitution or laws or opposition etc.)

Fault

A fracture in the rocks that make up the Earth's crust

Strike-slip fault

A fault along which the movement is horizontal

Reverse fault

A fault in which the material above the fault plane moves up in relation to the material below

Cross cutting

A principle of relative dating which states that a rock or fault is younger than any rock or fault through which it cuts

accretionary wedge

Along some subduction zones, sediments from the ocean floor and pieces of oceanic crust are scraped from the descending oceanic plate and plastered against the edge of the overriding plate. This chaotic accumulation of deformed sediment and scraps of oceanic crust is called

Salinity (seawater density)

An increase in salinity adds dissolved substances and results in an increase in seawater density

Parent/Daughter Isotopes

An unstable (radioactive) isotope is referred to as the parent. The isotopes resulting from the decay of the parent are the daughter products

How faults form

Brittle deformation results in the fracturing of rock material. Fractures in the crust along which appreciable displacement has taken place are called faults.

Reverse/Thrust Faults

Compressional forces associated with continental collisions that result in mountain building generate numerous reverse faults and thrust faults.

Depth (seawater density)

Deep water is denser than shallow water. The water molecules are packed together more tightly because of the weight of water above pushing down.

Absolute dating

Determining the number of years that have elapsed since an event occurred or the specific time when that event occurred

epicenter

Earth's surface directly above the hypocenter

Andesitic composition

Forms composite cones

Rhyolitic composition

Forms pyroclastic flows, lava domes

Basaltic composition

Forms shield volcanoes, basalt plateaus, and cinder cones

Salinity (seawater density)

High salinity makes water denser. This is because there is more salt packed into the water.

Temperature (seawater density)

High temperature makes water less dense. As water gets warmer, its molecules spread out, so it becomes less dense. As it gets colder, it becomes denser.

Original horizontality

If sedimentary rock layers are tilted, they must have moved after they were deposited

Seismic Waves

Large earthquakes release huge amounts of stored-up energy as seismic waves—a form of energy that travels through the lithosphere and Earth's interior. -The energy carried by these waves causes the material that transmits them to shake.

Seawater density

Seawater density is influenced by two main factors: salinity and temperature.

Gas (eruption)

The amount of dissolved gas in the magma provides the driving force for explosive eruptions

Half-life

The amount of time that it takes for half of the parent isotope to decay into daughter isotopes is called the half-life of an isotope

Parent/Daughter Isotope

The atomic nucleus that decays is called the parent isotope. The product of the decay is called the daughter isotope.

Focus (Hypocenter)

The point within the Earth where an earthquake rupture starts

subduction erosion

The opposite process, characterizes many other active continental margins. Rather than sediment accumulating along the front of the overriding plate, sediment and rock are scraped off the bottom of the overriding plate and transported into the mantle by the subducting plate.

Epicenter

The point at the surface of the Earth above the focus

Epicenter

The point on Earth's surface directly above the hypocenter is called the epicenter

Radioactive decay

The process by which unstable isotopes transform to stable isotopes of the same or different elements by a change in the number of protons and neutrons in the atomic nucleus

stratigraphy

The study of rock strata is called stratigraphy. The laws of stratigraphy can help scientists understand Earth's past.

What is an earthquake?

The sudden movement of one block of rock slipping past another along a fault (fractures in the earth's crust)

Strike-slip fault

When rocks on either side of a nearly vertical fault plane move horizontally

Fault creep

gradual displacement along a fault; occurs with little noticeable seismic activity

Reverse Faults

one in which the hanging wall moves up relative to the footwall.

normal fault

one in which the rocks above the fault plane, or hanging wall, move down relative to the rocks below the fault plane, or footwall

Superposition

refers to the position of rock layers and their relative ages.