Chapter 11: The Dynamic Planet

rigid lithosphere

"floats" or moves about on the slowly flowing asthenosphere, creating the movement of tectonic plates

Conservative/transform margins

mainly found on the ocean floor, where they offset mid ocean ridges and enable to ocean to spread at different rates.

foreshocks

minor shocks that precede major earthquakes

"the continental drift"

modern continents formed a single landmass in the past considered wrong bc both continents and ocean floor form solid plates, which "float" on the asthenosphere, the underlying rock that is under such tremendous heat and pressure that it behaves as an extremely viscous liquid

seafloor spreading

a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.

Abraham Ortelius 1596

noted that the coastlines of the continents appear to fit together

Peripheral (Pro) foreland basins

occur on the plate that is subducted or underthrust during plate collision

Retroarc (Retro) foreland basins

occur on the plate that overrides during plate convergence or collision

oceanic-continental convergence

oceanic lithosphere will always subduct below the continental lithosphere, caused by the density difference between the oceanic (3.0 g/cm3) and continental (2.7 g/cm3) lithosphere, oceanic plate melts and turns into hot magma which burns its way through the continental plate → creating a volcano and causing many earthquakes

seismic

of or relating to earthquakes or other vibrations of the earth and its crust

hypsometry

the measurement of land elevation relative to sea level

epicenter

the place directly above the focus on top of the ground

focus

the spot underground where the rocks break

isostasy

the state of gravitational equilibrium between Earth's crust and mantle such that the crust "floats" at an elevation that depends on its thickness and density

orogeny

"mountain building"- Tectonic plates break apart and diverge where the mantle beneath is upwelling. In such regions mid-ocean ridges develop, and new lithosphere and crust form to replace the material that is moving away. Where plates converge, usually where the mantle is downwelling, one plate is forced beneath another.

Brian Harland

(1964) was the first to provide concrete evidence for glaciers in tropical regions, when he presented palaeomagnetic data that illustrated the presence of glacial tillites in Svalbard and Greenland

vessel Glomar Challenger 1968

(in mid-ocean ridge between South America and Africa) collected core samples obtained from drilling revealed that rocks close to mid-ocean ridges are younger than rocks that are farther away from the ridges.

Wilson cycle

(of seabed expansion and contraction) named after John ('Jock') Tuzo Wilson. It has 6 steps: -Continental rifting -Formation of spreading center -Opening of ocean basin -Onset of subduction -Contraction of ocean basin -Continental collision

three sources of mantle convection

-"Primordial" heat (left over from the accretion and differentiation that led to the formation of Earth's core): 20-50% of the heat -Heating due to the decay of radioactive isotopes (mainly potassium, thorium, and uranium): 50-80% -tidal friction from the Moon's pull on the Earth: about 10%

Describe what steps that lead to an earthquake

-(stick-slip behavior) Once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. -continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy. -energy released as a combination of radiated elastic strain seismic waves (frictional heating of the fault surface) and cracking of the rock → earthquake

what happens to earthquake energy?

-10% or less of an earthquake's total energy is radiated as seismic energy -most energy is used to power the earthquake fracture growth or is converted into heat generated by friction -earthquakes lower the Earth's available elastic potential energy and raise its temperature

Ridge push (sliding plate force)

-As molten magma rises at a mid-ocean ridge, it heats the rocks around it → expands the lithosphere and asthenosphere at the ridge, pushing them above the surrounding ocean floor -As time passes, the heated rocks cool and their density increases → gravity pulls the weighty lithosphere away from the mid-ocean ridge, down the sloping asthenosphere, which, in turn, allows new molten magma to well up. This fresh magma will eventually become new lithosphere. -The cooling rock exerts a force (ridge push) on spreading lithospheric plates, helping to drive their movements. -Gravitational force that causes a plate to move away from the crest of an ocean ridge, and into a subduction zone

divergent plate boundaries

-At the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. -the crust is very thin at these ridges due to the pull of the tectonic plates

continental lithosphere

-Average density: 2.7 g/cm3 -also called the continental crust -layer of igneous, sedimentary rock that forms the continents and the continental shelves, consists mostly of granitic rock

oceanic lithosphere

-Average density: 2.9 g/cm3 -exists in the ocean basins (mean density of about 2.9 grams per cubic centimeter) -consists mainly of mafic crust and ultramafic mantle (peridotite) -denser than continental lithosphere -thickens as it ages and moves away from the mid-ocean ridge, occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle and causes the oceanic lithosphere to become increasingly thick and dense with age.

inner core

-Earth's innermost part believed to be primarily a solid ball with a radius of about 1,220 kilometers (760 miles) -composed of an iron-nickel alloy and some lights -elements (e.g. silicon, oxygen, sulfur) -temperature at the inner core boundary is -approx 5700 K (5400 °C)

Rodinia

-Formed 1 Billion Years Ago -one of the two true "super" continents. -Gaining this title simply because it was massive, and contained many of the land masses we know today - but all mashed together into one. -formed at c. 1.0 Ga by accretion and collision of fragments produced by breakup of an older supercontinent, Columbia, assembled by global-scale 2.0-1.8 Ga collisional events

Colombia

-Formed 1.8 Billion Years Ago, Paleoproterozoic Era -consisted of proto-cratons that made up the cores of the continents of Laurentia, Baltica, Ukrainian Shield,Amazonian Shield, Australia, and possibly Siberia, North China, and Kalaharia as well. -When it began to break up, it is thought that its pieces began moving around independently for several hundred million years and then, about a billion years ago, the band got back together and formed our next super: Rodinia.

Pangea

-Formed 300 Million Years Ago -existed during the late Paleozoic and early Mesozoic eras -During the Early Permian, the northwestern coastline of Gondwana smashed into the Euramerican continent. With the fusion of the Angaran part of Siberia to this combined landmass, the assembly of Pangea was pretty much done becoming 'super'. -much of Pangaea was in the southern hemisphere and surrounded by a super ocean, Panthalassa. -Pangaea was the last supercontinent to have existed -It began to break apart about 200 million years ago, during the Early Jurassic, eventually forming the modern continents and the Atlantic and Indian Oceans.

Pannotia

-Formed 600 Million Years Ago, formed at the end of the Precambrian -relatively short-lived Neoproterozoic supercontinent -formed during the Pan-African orogeny (650-500 Ma) and broke apart 560 Ma with the opening of the Iapetus Ocean -formed when Laurentia was located adjacent to the two major South American cratons, Amazonia and Río de la Plata. -The opening of the Iapetus Ocean separated Laurentia from Baltica, Amazonia, and Río de la Plata. -would eventually split into pieces - Laurentia, Siberia and Baltica with the main landmass of Gondwana to the south. -shapes of today's continents start to become recognizable.

Kenorland

-Formed: 2.7 Billion Years Ago, during the Neoarchaean Era -thought to have been made up from multiple smaller cratons -comprised what later became Laurentia, Baltica, Western Australia and Kalaharia -formed as a result of a series of accretion events and the formation of new continental crust -it was mostly all volcanic/igneous activity all the time, until those cratons started to collide. -When Kenorland started to break up, the oceans were just beginning to oxygenate and this is the point when the "snowball earth" theory takes place.

Ur

-Formed: 3 Billion Years Ago, Archean eon -first definitively known continent, despite being smaller at the time than Australia is now. -Ur is considered to be the first supercontinent although it's smaller than present-day Australia -broke apart about 208 million years ago into Laurasia and Gondwanaland. -can now find the remains of Ur in parts of Africa, Australia, India, and Madagascar

magnetization of new crust with Earth's geomagnetic field 1963

-Frederick J. Vine, Drummond H. Matthews, & Laurence W. Morley suggested that new crust would have a magnetization aligned with Earth's geomagnetic field. Over a geologic time, this would appear as bands of crust that exhibit alternating patterns of magnetic polarity. This provided more evidence that Earth's plates separate at mid-ocean ridges.

seafloor spreading 1960

-Harry H. Hess developed the idea that oceanic crust forms along mid-ocean ridges and spreads out laterally away from the ridges. -Robert S. Dietz named the phenomenon seafloor spreading. -helped develop modern theory of plate tectonics.

flux melting

-Melting aided by the addition of water or other fluid -the addition of water to the already hot mantle rocks lowers their melting temperature resulting in partial melting of ultramafic mantle rocks to yield mafic magma.

lithosphere

-Most rigid layer -includes the crust and the uppermost mantle, which -constitute the hard and rigid outer layer of the Earth -about 44 to 62 miles thick -subdivided into tectonic plates

convergent boundary

-Occurs when two plates come together: the impact of the two colliding plates buckles the edge of one or both plates up into a rugged mountain range, and sometimes bends the other down into a deep seafloor trench. -earthquakes and volcanoes are common near these boundaries

2 hypotheses explaining origins of hotspots

-One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core-mantle boundary. -Another suggests that lithospheric extension permits the passive rising of melt from shallow depths. It considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all.

mantle

-Solid -average thickness of 2,886 kilometres (1,793 mi) -makes up about 84% of Earth's volume -temperatures range between 500 to 900 °C at the upper boundary with the crust - over 4,000 °C at the boundary with the core -top of the mantle is defined by a sudden increase in seismic velocity (Mohorovičić to Moho) -upper mantle (starting at the Moho, or base of the crust around 7 to 35 km (4.3 to 21.7 mi) downward to 410 km (250 mi) -the transition zone (410-660 km or 250-410 mi) -the lower mantle (660-2,891 km or 410-1,796 mi) anomalous core-mantle boundary with a variable thickness (on average ~200 km (120 mi) thick) -Composition: O , Mg, Si , Fe, Ca, Al, Na, K -elements bounded together in the form of silicate rocks in the form of oxides.

Vaalbara

-THEORY Formed: 3.3 Billion Years Ago ?, Archean eon -Archean supercontinent that consisted of the Kaapvaal craton, today located in eastern South Africa, and the Pilbara carton -today found in north-western Western Australia -two oldest cratons on the planet both have the oldest rock dated, so assumptions are made about what Vaalbara might have looked like based only on these two patches of oldness. -evidence shows the possible existence of Vaalbara & indicates that it started to break up after 2.5 billion years.

transform boundary

-Two plates sliding past each other -neither create nor destroy lithosphere, relative motion is mainly horizontal - sinistral (left lateral) or dextral (right lateral) -Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon Earthquakes occur, no magma is formed, crust is cracked and broken at transform margins but is not created or destroyed

outer core

-a fluid layer about 2,300 km (1,400 mi) thick -composed of mostly iron and nickel -outer boundary lies 2,890 km (1,800 mi) beneath Earth's surface. -the transition between the inner core and outer core is located approximately 5,150 km (3,200 mi) beneath the Earth's surface -3,000-4,500 K near the inner core

terranes

-a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate -crustal block or fragment preserves its own distinctive geologic history -the suture zone between a terrane and the crust it attaches to is usually identifiable as a fault

graben

-a graben is a valley with a distinct escarpment on each side caused by the displacement of a block of land downward -produced from parallel normal faults, where the displacement of the hanging wall is downward, while that of the footwall is upward

monogenetic volcanic fields

-a group of small monogenetic volcanoes, each of which erupts only once -many are cinder cones

horst

-a horst is the raised fault block bounded by normal faults or graben. -a raised block of the Earth's crust that has lifted, or has remained stationary, while the land on either side has subsided

suture

-a joining together along a major fault zone, of separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories. -represented on the surface by an orogen or mountain range.

craton

-a large, stable block of the earth's crust forming the nucleus of a continent -is used to distinguish the stable portion of the continental crust from regions that are more geologically active and unstable

rift basin

-a linear zone where the Earth's crust and lithosphere are being pulled apart -occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates -Sedimentary rocks deposit into the rift valley in ideal environments for limestones to form

rift valleys

-a linear-shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault

asthenosphere

-a part of the upper mantle just below the lithosphere that is involved in plate tectonic movement and isostatic adjustments -approx. 80 and 200 km (50 and 120 miles) below the surface -source region of mid-ocean ridge basalt (MORB) -extends from about 100 km (60 miles) to about 700 km (450 miles) below Earth's surface about 62 miles thick -crust heats up to 1300° C, 1,600 degrees Fahrenheit but does not rise above 6,700 degrees F -made up of mafic and ultramafic rocks, same material as the upper lithosphere, but the material in the asthenosphere is in a plastic, viscous state and moves around much more readily than the material in the lithosphere.

tectonostratigraphic terrane

-a piece of crust which has been transported sideways, usually as part of a larger plate, and is relatively buoyant due to thickness or low density. -When the plate of which it was a part subducted under another plate, the terrane failed to subduct, detached from its transporting plate, and accreted onto the overriding plate. -Therefore, the terrane transferred from one plate to the other.

associated faults

-a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock mass movement. -Large faults within the Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates. -Energy release associated with rapid movement on active faults is the cause of most earthquakes

volcanoes

-a rupture in the crust of Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface -found where tectonic plates are diverging or converging or volcanism away from plate boundaries has also been explained as mantle plumes -80% of the volcanic eruptions on Earth take place in the ocean

glaciation

-an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances

mantle plumes

-an upwelling of abnormally hot rock within the Earth's mantle -Once the temperature increases sufficiently to lower the rock density, a column of the hotter-than-normal rock (perhaps 2,000 kilometers in diameter) starts to rise very slowly through the surrounding mantle rocks. -Eventually, the rising column of hot rock reaches the base of the lithosphere, where it spreads out, forming a mushroom-shaped cap to the plume → plume spreads → The overlying lithosphere is pushed up → Heat transferred from the plume raises the temperature in the lower lithosphere to above melting point, and magma chambers form that feed volcanoes at the surface, AKA a hot spot. -a string of volcanoes is created. -secondary way that Earth loses heat

lava domes

-built by slow eruptions of highly viscous lava sometimes formed within the crater of a previous volcanic eruption -can also form independently -can produce violent, explosive eruptions, but their lava generally DOES NOT FLOW FAR from the originating vent.

foreland basin

-develops adjacent and parallel to a mountain belt -Form by subduction, the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend (lithospheric flexure). -width and depth determined by the flexural rigidity of the underlying lithosphere, and the characteristics of the mountain belt. -filled with sediments which erode from the adjacent mountain belt -in the early stages, said to be underfilled. -During this stage, deep water and commonly marine sediments, known as flysch, are deposited. -Eventually, the basin becomes completely filled. At this point, the basin enters the overfilled stage and deposition of terrestrial clastic sediments occurs,known as molasse. -Sediment fill within the foredeep acts as an additional load on the continental lithosphere.

Where are volcanoes found?

-divergent plate boundaries -convergent plate boundaries -hot spots

tectonic plates

-enormous sections of rock that make up the Earth's crust. -two types: continental, oceanic -are propelled over the surface of the planet during millions of years by currents of magma far below -weight of the oceans compress oceanic plates into smaller volumes → thinner and denser than continental plates (which are above ocean level)

polygenetic volcanoes

-erupt repeatedly over a period of time.

aulacogens

-failed arm of a triple junction of a plate tectonics rift system -A triple junction beneath a continental plate initiates a three way breakup of the continental plate. As the continental break-up develops one of the three spreading ridges typically fails or stops spreading. The resulting failed rift is called an aulacogen and becomes a filled graben system within the continental lithosphere. -The crust in an aulacogen region remains weakened by previous rifting activity → seismic activity and volcanic activity may re-occur subsequently from time to time -remain places of weakness but can reactivate into active rift valleys again

shield volcanoes

-formed by the eruption of low-viscosity lava that can flow a great distance from a vent. -more common in oceanic than continental settings

cryptodomes

-formed when viscous lava is forced upward causing the surface to bulge -lava beneath the surface of the mountain created an upward bulge which slid down the north side of the mountain

backarc basin

-found at some convergent plate boundaries mainly in the Western Pacific ocean -characterized by asymmetric seafloor spreading -Sedimentation is strongly asymmetric, with most of the sediment supplied from the active magmatic arc which regresses in step with the rollback of the trench. -formed by the process of back-arc spreading -The arc crust is under extension/ rifting as a result of the sinking of the subducting slab. -In subduction boundaries, sediment is shed off the volcanic mountains. This sediment is poorly weathered, and contains many black minerals and volcanic rock fragments. -In ocean-ocean subduction boundaries, the sediment is deposited in the forearc on the opposite side of the volcanic island chain from the trench.

mass wasting

-geomorphic process by which soil, sand, regolith, and rock move downslope typically as a mass, largely under the force of gravity, but frequently affected by water and water content as in submarine environments and mudflows. -Types of mass wasting: creep, slides, flows, topples, and falls

oblique slip

-has a component of dip-slip and a component of strike-slip

dip-slip

-inclined fractures where the blocks have mostly shifted vertically. -Normal: If the rock mass above an inclined fault moves down -Reverse: if the rock above the fault moves up -A thrust fault is a reverse fault with a dip of 45 degrees or less

Synthetic and antithetic faults

-minor faults associated with a major fault. -Synthetic faults dip in the same direction as the major fault -antithetic faults dip in the opposite direction. -may be accompanied by rollover anticlines

earthquakes

-occur along the boundaries of Earth's tectonic plates or in the middle of a plate when there is a fault (see faults) -occur when two blocks of earth suddenly slip past each other -occur as a result of tectonic plates colliding and volcanic eruption. -occur when rock underground suddenly breaks along a fault. -sudden release of energy causes the seismic waves that make the ground shake.

ring fault

-occur within collapsed volcanic calderas and the sites of bolide strikes, such as the Chesapeake Bay impact crater -may be filled by ring dikes

Slab/trench suction

-occurs when a subducting slab drives flow in the nearby mantle → This flow then exerts shear tractions on nearby plates. -This driving force is important when the slabs (or portions thereof) are not strongly attached to the rest of their respective tectonic plate. They cause both the subducting and overriding plate to move in the direction of the subduction zone. -weakest of the three major forces, product of slab pull and ridge push.

divergent boundary

-occurs when two tectonic plates move away from each other and the space is filled with new crustal material sourced from molten magma that forms below -frequent earthquakes strike along the rift; beneath the rift, magma rises from the mantle into the gap and hardens into basalt -also form volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill

elastic rebound theory

-process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure

volcanic cones/ cinder cones

-result from eruptions of mostly small pieces of scoria and pyroclastics that build up around the vent, most only erupt once -can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30-400 m high -Cinder cones may form as flank vents on larger volcanoes, or occur on their own.

oceanic crust

-rocks rich in magnesium and silicate minerals -Thickness: 5-10 km (3-6 mi.) -Average density: 2.9 g/cm3 -Elevation: 10,000 ft (3,048 m) below sea level -result of erupted mantle material originating from below the plate, cooled and in most instances, modified chemically by seawater, subduction process forms new oceanic crust -younger than continental crust -60% of Earth's surface -topmost layer - 500 meters thick, made up of basaltic rocks in the shape of pillows and sheets. -lower layer made up of two sub-layers that cover a thickness of 4.5 kilometers, made up of gabbros (mixed coarse grains of minerals that contain pockets or chambers of lava that finds its way up to the floor of the ocean)

continental crust

-rocks rich of aluminum and silicon minerals -made up of 15 tectonic plates that float on the viscous (liquid-solid) rock at the very top of the Earth's mantle -rocks that form continents and continental shelves -Thickness: 30-50 km (20-30 mi.) -Elevation: 2,000 ft (609 m) above sea level -Average density: 2.7 g/cm3 -created by plate tectonics-at convergent plate boundaries, where tectonic plates crash into each other, continental crust is thrust up in the process of orogeny (mountain-building). -derives from the fractional differentiation of oceanic crust over many long periods of times -40% of Earth's surface -not all continental crust is above sea level

Name types of volcanoes

-shield volcanoes -lave domes -cryptodomes -volcanic cones/cinder cones -strato volcanoes -super volcanoes -submarine volcanoes -subglacial volcanoes -mud volcanoes

listric fault

-similar to normal faults but the fault plane curves, the dip being steeper near the surface, then shallower with increased depth. -The dip may flatten into a sub-horizontal décollement, resulting in horizontal slip on a horizontal plane.

subduction zones

-sites that have a high rate of volcanism, earthquakes, and mountain building -where Earth's lithosphere, oceanic crust, sedimentary layers and some trapped water are recycled into the deep mantle

mantle convection

-slow creeping motion of Earth's solid silicate mantle caused by convection currents carrying heat from the interior of the Earth to the surface -main mechanism by which this heat escapes from the interior of Earth.

stick slip phenomenon

-spontaneous jerking motion that can occur while two objects are sliding over each other

what are the 6 faults?

-strike slip -dip slip -oblique slip -listric fault -ring fault

subduction

-takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced or sinks due to gravity into the mantle -Process: The descending slab, the subducting plate, is over-ridden by the leading edge of the other plate. The slab sinks at an angle of approximately twenty-five to forty-five degrees to Earth's surface. This sinking is driven by the temperature difference between the subducting oceanic lithosphere and the surrounding mantle asthenosphere, as the colder oceanic lithosphere is, on average, denser. At a depth of approximately 80-120 kilometers, the basalt of the oceanic crust is converted to a metamorphic rock called eclogite. At that point, the density of the oceanic crust increases and provides additional negative buoyancy (downwards force)

stratovolcanoes

-tall conical mountains composed of lava flows and other ejecta in alternate layers that are created from multiple structures during different kinds of eruptions. -made of cinders, ash, and lava: cindoors and ash pile on top of each other, lava flows on top of the ash, where it cools and hardens, and then the process repeats. -have greater pressure build up from the underlying lava flow than shield volcanoes -fissure vents and monogenetic volcanic fields (volcanic cones) have more powerful eruptions, as they are many times under extension -steeper than shield volcanoes -with slopes of 30-35° compared to slopes of generally 5-10°

isostatic adjustment

-the basins in the ocean have increased in size since the last cycle of glaciers came to an end. -results from the recovery of the Earth's surface from the once heavy, thick ice sheets that covered the majority of Europe and North America.

strike slip

-the fault surface is usually near vertical and the footwall moves either left or right or laterally with very little vertical motion. -those with left-lateral motion are also known as sinistral faults -those with right-lateral motion are also known as dextral faults. -transform faults form a plate boundary.

convergent plate boundaries

-the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. -using flux melting, water released from the subducting plate lowers the melting temperature of the overlying mantle wedge, creating magma. -created magma tends to be very viscous due to its high silica content, so it often does not reach the surface but cools at depth. -when magma reaches surface, a volcano is formed.

triple junction

-the point where the boundaries of three tectonic plates meet. -at the triple junction each of the three boundaries will be one of 3 types - a ridge (R), trench (T) or transform fault (F)

post glacial rebound

-the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period -the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets -causes crustal motion

isostatic depression

-the sinking of large parts of the Earth's crust into the asthenosphere. -caused by a heavy weight placed on the Earth's surface & by the heavy weight of glacial ice due to continental glaciation.

crust

-very thin compared to other 3 layers -made up different types of rocks (igneous, sedimentary, and metamorphic) -temperature increases with depth -made up of mostly O, Si, Al, Fe, Ce, Na, K, and Mg

hot spots

-volcanic area believed to be formed by mantle plumes, which are hypothesized to be columns of hot material rising from the core-mantle boundary in a fixed space that causes large-volume melting. -Because tectonic plates move across them, each volcano becomes dormant and is eventually reformed as the plate advances over the postulated plume.

hot spots

-volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle may be on, near to, or far from tectonic plate boundaries.

intermountain basin

-wide valley between mountain ranges formation of mountains- large-scale movements of the Earth's crust (plate tectonics). -Folding, faulting, volcanic activity, igneous intrusion and metamorphism can all be parts of the orogenic process of mountain building. -partly filled with alluvium

3 main forces

1. Slab pull (strongest) 2. Ridge push 3. Slab-trench suction (weakest)

hydroacoustic signals mid 1960s

A global network of sensors designed to detect hydroacoustic signals that recorded earthquake activity. Scientists later found that earthquakes and volcanic activity occur almost exclusively at the edges of tectonic plates.

Convergent/Destructive Margins

As oceanic lithosphere cools, it becomes denser, and the further away from the plate boundary it moves, the thicker it becomes. At a convergent plate boundary the oceanic lithosphere sinks beneath the adjacent plate in a process known as 'subduction'.

what is an example of mid-oceanic ridge being above sea level?

Ex: Iceland -volcanic islands form

what is an example of volcanic activity being submarine?

Ex: West Mata volcano Most divergent boundaries are at the bottom of oceans, so most volcano activity is submarine forming new seafloor

supercratons

In more recent works geologists often refer to both Ur and other proposed Archaean continental assemblages as supercratons.

Divergent/Constructive Margins

In the oceans, this has produced the mid ocean ridge system (a global range of underwater mountains)

oceanographic vessels 1950s

Kinda like submarines that mapped the ocean floor and provided data on the topographic features of the ocean basin. This led to the discovery of mid-ocean ridges. These underwater mountain ranges encircling the planet form as Earth's plates separate.

stratum

a layer or a series of layers of rock in the ground

mountain formation

Tectonic plates break apart and diverge where the mantle beneath is upwelling. -mid-ocean ridges develop, and new lithosphere and crust form to replace the material that is moving away. -where plates converge, one plate is forced beneath another

Slab pull

The force that the sinking edge of the plate exerts on the rest of the plate/pulling force exerted by a cold, dense oceanic plate plunging into the mantle due to its own weight As lithospheric plates move away from midocean ridges, they cool and become denser. They eventually become more dense than the underlying hot mantle. After subducted, cool, dense lithosphere sinks into the mantle under its own weight. This helps to pull the rest of the plate down with it.

slab

The lithosphere is broken up into slabs called lithospheric plates or tectonic plates

fissure vents

a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few meters wide and may be many kilometers long

basalt

a dark dense rock that underlies the ocean floor

strike slip fault

a fault in which rock strata are displaced mainly in a horizontal direction, parallel to the line of the fault.

aftershocks

after the main shock, further movements occur as the rock masses settle in their new positions

continental shelves

areas of shallow seabed close to their shores

upper part of the asthenosphere

believed to be the zone upon which the great rigid and brittle lithospheric plates of the Earth's crust move about

orogenic plates

develop when a continental plate is crumpled and is pushed upwards to form mountain ranges

seismic tomography mid 1970s

enables scientists to investigate the dynamic processes in the deep interior of Earth. Scientists created three-dimensional images of Earth's interior by combining information from many earthquakes using an approach similar to computed tomography (CT) scanning.

Alfred Wegener 1912

father of the theory he called "the continental drift"

Igneous

form from the cooling of magma deep inside the earth, often have large crystals

Metamorphic

formed through the change (metamorphosis) of igneous and sedimentary rocks, can form both underground and at the surface

Sedimentary

formed through the solidification of sediment, can be based off of organic remains (such as limestone) or just form from the cementing of other rocks

SedEx (sedimentary exhalative deposits) mineral deposits

found mainly in continental rift settings Continental rifts are the sites of significant oil and gas accumulations,

continental- continental convergence

happens where 2 continental plates collide and push up creating mountain ranges

oceanic-oceanic convergence

happens where 2 oceanic plates push against one another, causing the colder, denser, older plate to buckle up and sink into the mantle. Hot magma comes from where the plate sank, creating new crust.

sedimentary rocks associated with continental rifts

host deposits of both minerals and hydrocarbons

subduction process

is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced or sinks due to gravity into the mantle

fault plane

planar surface along which there is slip during an earthquake.

accreting terranes

portions of continental crust which have rifted off another continental mass and been transported surrounded by oceanic crust, or old island arcs formed at some distant subduction zone

largest mantle plumes form

presumed to form where a large volume of mantle rock is heated at the core-mantle boundary, about 1,800 miles below the surface, although smaller plumes may originate elsewhere within the mantle.

Arthur Holmes 1929

proposed that convection in the mantle is the force driving continental drift

back arc spreading

tensional forces caused by oceanic trench rollback (the oceanic trench is wandering in the seafloor direction) and the collapse of the edge of the continent

Laurentia

the core of today's North America and Greenland

"snowball earth theory"

the earth's surface was entirely frozen from pole to pole. Evidence of a Snowball Earth comes from the presence of glacial deposits around the world that date back to the Cryogenian period

transform fault

the fracture zone that forms a transform plate boundary, most are found in the ocean basin and connect offsets in the mid-ocean ridges

Baltica

today's Scandinavia and Baltic

earthquakes occur

when a fault ruptures and the accumulated strain is abruptly released