Geology Exam 1

Front 1

the phase trading space for time signifies what?

Back 1

different parts of a landscape can be used to infer how the landscape changes over time

Front 2

which of the following is NOT consistent with the progression through the rock cycle?

Back 2

solidification, melting, burial

Front 3

Which type of figure best portrays the shape of the land surface?

Back 3

topographic map

Front 4

what type of rock makes up ocean crust?

Back 4

ocean crust is made from mafic igneous rock (ie basalt and gabbro)

Front 5

What is the process that creates mafic igneous rocks at mid-ocean ridges?

Back 5

at mid ocean ridges the ocean crust is separating, creating a gap into which the aesthenosphere (weak rock mantle) flows. As the aesthenosphere flows upwards, it undergoes decompression melting which creates mafic magma. Ocean crust is then formed from mafic magma that has cooled into basalt and gabbro (mafic igneous rock)

Front 6

Which method allows us to get data from below the seafloor?

Back 6

drilling holes into the seafloor from ships

Front 7

why are mid-ocean ridges elevated?

Back 7

because they are underlain by new, hot and less dense ocean crust

Front 8

Which best describes decompression melting?

Back 8

lowering the melting temperature of a rock by lowering its pressure

Front 9

What type of plate boundary?

Back 9

this is a divergent plate boundary- specifically a continental rift. As at mid-ocean ridges, aesthenosphere is rising into the gap and magma is created by decompression melting. If the motion continues, the continents will separate and a new ocean basin will form in between them.

Front 10

why are there hydrothermal vents (hot springs) on mid ocean ridges?

Back 10

because normal faults and joints allow water to circulate in the new ocean crust

Front 11

why are there magnetic stripes on the ocean floor?

Back 11

because ocean crust records the earths magnetic field as it is formed

Front 12

describe how islands/seamounts form. Include how magma is created.

Back 12

magma is created by decompression melting. A rising hot plume of mantle creates a magma source. Magma then rises through the crust to create a new volcanic island. Plate motion then moves the island off the hotspot and as they cool, they sink becoming a seamount as a new island grows over the hotspot.

Front 13

Which part of the seafloor is deep and covered by thick sediment?

Back 13

abyssal plains

Front 14

which best describes the formation of a shield volcano?

Back 14

A volcano made from many fluid lava flows

Front 15

what is the most successful hypothesis for the formation of a coral atoll island?

Back 15

volcanic island forms and subsides below the surface

Front 16

Describe how subduction creates magma. How does this influence the volcanic hazard at subduction zones?

Back 16

subduction brings water into the mantle. H2O mixes with hot mantle and lowers its melting temperature causing it to melt (hydration melting)-the h2o stays with the magma, rapidly turning into steam as it leaves the volcano, creating explosive volcanism at the surface

Front 17

why is the oldest ocean crust only 180 myr old?

Back 17

because ocean crust is always subducted

Front 18

why is the pacific ocean surrounded by volcanoes?

Back 18

because it is surrounded by subduction zones

Front 19

which best describes a pyroclastic flow?

Back 19

a mix of hot gas, ash and rock flowing down the slopes of a volcano

Front 20

what type of magma creates a lava dome? what impact can it have on volcanic hazard?

Back 20

it is made from low gas, high silica viscous rhyolite magma. A lava dome overgrowing a volcanoes crater can collapse and cause pyroclastic flows. It can also block the throat of a volcano and lead to a more violent, explosive eruption with a new gas rich explosion coming from below.

Front 21

what best describes a lahar?

Back 21

a mix of ash, water and rock flowing down rivers around a volcano

Front 22

what best describes a volcanic caldera?

Back 22

a volcano that collapses after a large ash eruption

Front 23

which process creates the most tsunamis

Back 23

shallow subduction zone earthquakes

Front 24

describe the process of convection. How does this process relate to the creation and destruction of oceanic lithosphere?

Back 24

convection is the movement of heat by the movement of hot material to cold and vice versa. Ocean crust is created at mid ocean ridges by the upwelling of hot aesthenosphere and destroyed in subduction zones as cold ocean plate is recycled into the mantle

Front 25

why did the continental drift hypothesis fail?

Back 25

it did not explain the movement of the continents

Front 26

which is the strongest plate motion force?

Back 26

slab pull

Front 27

how is continental crust different from oceanic crust?

Back 27

it is thicker and less dense

primarily granite vs primarily basalt

Front 28

what does mapping volcanic deposits tell you about volcanic hazards?

Back 28

mapping volcanic hazards show you where different types of volcanic hazards have occurred in the past and how often they have occurred

Front 29

what did mapping reveal about the most dangerous volcanic hazard at mt rainier?

Back 29

showed that lava flows and pyroclastic flow stays close to the volcano while lahars can reach heavily populated areas like the city of tacoma.

Front 30

which natural hazards are most commonly associated with plate boundaries?

Back 30

volcanoes, earthquakes, and tsunamis

Front 31

which type of volcano monitoring helps determine if an explosion will be explosive?

Back 31

gas monitoring

Front 32

what are scorcia cones?

Back 32

volcanoes formed by erruptions of gas rich, and very fluid mafic basalt magma. gas pressure in magma propels the lava into the air.

Front 33

shield volcanoes

Back 33

have a low, dome shape. created by large flows of fluid, basalt lava flows

Front 34

how is ocean crust made?

Back 34

mafic ingneous rock formed when sea floor spreading creates conditions for decompression melting. Made at mid ocean ridges

Front 35

ocean basins

Back 35

created when continental rifting leads to the continent separating into two pieces with an ocean between them

Front 36

ocean sediments

Back 36

thickest on the edge of continents

Front 37

ocean plateau

Back 37

broad areas of very thick oceanic crust. Believed to form at hot spots, but from a series of fissures over a wide area

Front 38

viscosity

Back 38

the ability to resist flow. In lava, this is controlled by silica percentage. more silica = thicker, more viscous lava. Magma is most fluid when hot. As it cools, the silica percentage rises and the magma becomes more viscous

Front 39

motion of the pacific

Back 39

portions of earths surface are moving towards each other (converging)

Front 40

subduction

Back 40

as ocean crust and lithosphere cool and become more dense, they can sink back into the interior of the earth. Ocean trenches and explosive volcanoes mark subduction zones.

Front 41

hydration melting

Back 41

subducting ocean crust brings h2o into the mantle, which mixes with the hot mantle rock. This lowers the melting temperature of the mantle, causing part of it to melt. This h2o in the magma can cause extremely explosive eruptions

Front 42

composite volcanoes

Back 42

many subduction volcanoes are these classic, conical, symmetric volcanoes. They are made from many different volcanic rocks. generally have viscous lava flows.

Front 43

pyroclastic flows

Back 43

a hot, dense ash and rock cloud that flows down the volcano at speeds greater than 100 mph

Front 44

lahars

Back 44

ash and rock mixed with melted ice water to form a volcanic mudflow

Front 45

calderas

Back 45

collapse features that form after large ash and pumice eruptions that empty the lava chamber

Front 46

tsunamis

Back 46

mostly caused by shallow earthquakes at subduction zones. Between earthquakes, the overlying crust bends down and snaps up, creating a large wave in the ocean.

Front 47

deep earthquakes

Back 47

associated with subduction zones, they mark the location of subducting ocean plates

Front 48

divergent boundaires

Back 48

mid-ocean ridges and continental rifts. decompression melting produces basalt magma

Front 49

convergent boundaries

Back 49

subduction zones. hydration melting produces gas rich magma