Dynamic Planet - Vocab

Abraham Ortelius 1596

noted that the coastlines of the continents appear to fit together

Alfred Wegener 1912

father of the theory he called "the continental drift"

"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

stratum

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

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.

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

Arthur Holmes 1929

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

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.

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.

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.

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.

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.

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.

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

seismic

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

basalt

a dark dense rock that underlies the ocean floor

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

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

continental shelves

areas of shallow seabed close to their shores

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.

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)

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

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.

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

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.

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.

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

rigid lithosphere

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

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

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)

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)

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

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

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