Env 234 - Lecture 2

Front 1

what are igneous rocks made from?

Back 1

magma

Front 2

how are metamorphic rocks made?

Back 2

through high pressure

Front 3

what type of rocks are intrusive and extrusive?

Back 3

igneous

Front 4

what type of rocks are foliated and non-foliated

Back 4

metamorphic

Front 5

what is the outer ridge of the earth

Back 5

the rigid lithosphere (including crust)

Front 6

what does the lithosphere float atop of?

Back 6

asthenosphere

Front 7

what is the theory of plate techtonics?

Back 7

earth's lithosphere is divided into plates (like the shell of a cracked egg) that move relative to one another, and relative to the underlying asthenosphere

Front 8

what happens to plates as they move?

Back 8

their interiors remain relatively intact, while their boundaries undergo deformation

Front 9

what evidence is there for plate tectonics?

Back 9

continents were connected
-matching coastlines
-similar rocks, glacial features "cross" oceans
-same fossils

Front 10

what occurs at the edges of plates

Back 10

-earthquakes
-volcaoes
-mountain belts

Front 11

what is the ring of fire?

Back 11

the valcanoe distribution around the Pacific

Front 12

what are some examples of mountain belts

Back 12

alps and himalayas

Front 13

what are three different types of plate boundaries

Back 13

divergent
convergent
transform

Front 14

what is an example of divergent plate boundary

Back 14

two plates spreading apart in the mid-ocean ridge

Front 15

in a mid ocean ridge, what creates the rift?

Back 15

these rifts run along the axis of most mid-ocean ridges. the rift forms because large blocks of crust slip down as spreading occurs. this movement causes faulting, = frequent small to moderate sized earthquaques

Front 16

in an mid ocean ridge what happens as the plates move apart

Back 16

solid mantle in the asthenosphere rises towards the surface and partially melts in response to a decrease in pressure. the magama rises along condiduits accumulating magma in chambers beneath the rift, eventually becoming part of the oceanic lithosphere

Front 17

in mid ocean ridges what happens to the magma?

Back 17

much of it solidifies at depth, but some erupts onto sea floor, forming submarine lava flows. these eruptions create new ocean crust that is incorporated into the oceanic plates as they move apart.

Front 18

why are mid-ocean ridges elevated

Back 18

ridges consist of hotter, less dense materials (like magma). also the underlying lithosphere is thinner so it 'floats' higher on he asthenosphere. the evelvation decreases away from the ridge as the rocks cool and contracts, and as the less dense asthenosphere cools enough to become a part of the more dense lithosphere

Front 19

what is an example of a continental rift?

Back 19

african rift valley

Front 20

what type of plate boundary is a mid-ocean ridge an example of?

Back 20

divergent

Front 21

what type of plate boundary is continental rifting an example of?

Back 21

divergent

Front 22

what is the initial stage of continental rifting?

Back 22

broad uplife of the land surface and mantle-derived magma ascends into and pushes up the crust. the magma heats up and can melt parts of the continental crust creating more magma. heating of the crust causes it to expand creating more uplift

Front 23

in continental rifting what happens after uplift

Back 23

the uplift creating stretching of the crust which cause large crustal blocs to drop down into faults forming continental rift. the dropped blocks may form basins that can trap sediment and water creating lakes.

Front 24

what happens if there is deep rifting in a continental rift

Back 24

it causes solid mantle material in the asthenosphere to flow up and partially melt. the magma may solidify beneath the surace or erupt from volcaoes or fissures. the entire crust thins as it is pulled apart so the central rift becomes lower in elevation over time

Front 25

what happens in a continental rift if it continues to rift

Back 25

the continent splits into two pieces and a narrow ocean basin forms. as the edges move apart with the association of the heat from active spreading, the thinned crust cools and drops in eleveation, eventually below sea lvl

Front 26

in continental rifting what happens to the central rift

Back 26

the entire crust thins as it is pulled apart, so the central rift becomes lower in elevation over time

Front 27

what happens in continental rifting after the cooling crust drops below sea level?

Back 27

the continental margin ceases to be a plate boundary. a continental edge that lacks tectonic activity is called a passive margin

Front 28

in continental rifting what happens to the ocean basin with continuing seafloor spreading?

Back 28

the ocean basin becomes progressively wider, eventually becoming a broad ocean like the modern day Atlantic Ocian

Front 29

what is an example of early stages of rifting?

Back 29

East African Rift

Front 30

what is subduction?

Back 30

one plate pushes beneath another, creating ocean trench, colcanic arcs, mountains

Front 31

what are types of convergent plates?

Back 31

ocean-ocean
ocean-continent

Front 32

what is subduction

Back 32

the process of one plate sliding beneath another

Front 33

what is the subduction zone

Back 33

the zone around the downward-moving plate

Front 34

what occurs in the subduction zones

Back 34

many large earthquakes

Front 35

what happens with the convergence of two oceanic plates

Back 35

it forms an ocean-ocean convergent boundary. one plate bends and slides beneath the other pleate along an inclined zone

Front 36

what forms as subducting plate moves down

Back 36

an oceanic trench
sediment and slices of oceanic crust collect in the trench, forming a wedge called an accretionary prism (a*prism signifies that mateerial is being added (accreted) over time to the wedge or prism-shaped region

Front 37

what happens to the plate as it subducts

Back 37

its temperature increasing, releasing water from minerals in subducting plate. this water causes melting in the overlying asthenosphere and the resulting magma is buoyant and rising into the overlying plate

Front 38

what happens to the magma creating by the subducting plate?

Back 38

some of it erupts, intially under the ocean then as volcanoes that rise above the sea. over time it creates a curving belt of islands called an island arc. the area between the island arc and the ocean trench accumulates sediment, most of which comes from volcano eruptions and erosion

Front 39

in ocean-ocean convergent boundaries what happens to the magma that solidifies at depth

Back 39

it adds to the volume of the crust. over time, the crust gets thicker and becomes transition beween ocean and continental . volcanic islands join to form more continuous strips of land

Front 40

what happens in he convergence of an oceanic and a continental place

Back 40

it forms an ocean-continent convergent boundary. the denser oceanic plate subduct beneath the more buoyant continental plate

Front 41

what marks the plate boundary between an ocean-continental convergent boundary

Back 41

an oceanic trench which receives sediment from the adjacent continent. this sediment and material scraped off the oceanic plate form and accretionary prism

Front 42

do volcanoes form in ocean-continental convergent boundaries

Back 42

yes, the form on the surface of the overriding continental plate

Front 43

what occurs to the continental plate in an ocean-continental convergent boundary

Back 43

compression squeezes the crust for 100km into the continent. the crust deforms and thickens, resulting in uplife. uplift and volcanoes may produce a high mountain range

Front 44

How is magma form in ocean-continental convergent boundary

Back 44

it forms by melting of the asthenosphere above the subduction ones. it can solidify at depth, rise into the overlying continental crust before solidifying or reach the surface and cause a volcanic eruption