Lecture Quiz 2

Question 1

the half life of a radioactive element is

Answer 1

the time required for half the parent to decay to the daughter

Question 2

a plate boundary where the plates are moving away from each other is called

Answer 2

divergent

Question 3

a surface in a vertical sequence of rocks where time is not represented by rock is called

Answer 3

unconformity

Question 4

calderas or supervolcanoes are very dangerous because

Answer 4

the magma is very silica rich, the amount of ash erupted would be very large, the eruption would be regional

Question 5

igneous rocks typically form at and volcanic activity takes place at

Answer 5

convergent boundaries, divergent boundaries, mantle hot spots

Question 6

the most dangerous process associated with composite cones in close proximity to coastal cities is

Answer 6

mud flows

Question 7

earthquake magnitude

Answer 7

is measured on the Richter scale, is calibrated for distance

Question 8

most of the structural damage from earthquakes is caused by

Answer 8

surface waves

Question 9

p waves travel through all types of materials and are transmitted via

Answer 9

compression

Question 10

three sites (L1 L2 L3) record earthquakes intensity and earthquake magnitude for the same earthquake. L1 is located closest to the earthquake focus, L3 is farthest away. the intensity values are greatest at _____ and the earthquake magnitude(calculated using seismograms) _____

Answer 10

L1; is the same at each site

Question 11

the slopes of a shield volcano are not as steep as a composite cone because

Answer 11

the lava is less viscous

Question 12

seismic waves particularly body waves give us a great deal of information about the interior of the earth, and in fact we know that the outer core is a liquid because

Answer 12

S waves disappear

Question 13

wegener’s idea of continental drift was rejected because

Answer 13

although he had plenty of evidence, it lacked a suitable mechanism

Question 14

A tectonic plate boundary in which the plates are moving towards the boundary commonly destroying oceanic crust and generating intermediate magma that rises to become stratovolcanoes/composite cones

Answer 14

ocean continent convergent, subduction zones, ocean ocean convergent

Question 15

melting the material that will become magma and eventually igneous rocks and volcanic activity inloves

Answer 15

bringing heat up with convection, taking the crust deeper with subduction

Question 16

the main driving force that results in the movement of the crustal plates is

Answer 16

mantle convection

Question 17

although it was a much smaller event, the earthquake in Haiti resulted in much greater numbers in terms of loss of life than in Chile because

Answer 17

building design, lack of building codes

Question 18

cone shaped volcanoes occur because

Answer 18

volcanic ash has a high angle of repose, the magma is more viscous

Question 19

the driving force behind a volcanic eruption, or the process that forces magma out of the ground

Answer 19

gasses bubbling out of solution

Question 20

volcanic eruptions can change climate because

Answer 20

volcanic ash in the atmosphere blocks in the sun

Question 21

the overall explosive nature of a volcanic eruption can be predicted by

Answer 21

the amount of silica in magma

Question 22

stratovolcanoes form as______ build up over time

Answer 22

alternating layers of ash and viscous lava

Question 23

the modern evidence for plate tectonics includes

Answer 23

the geography of the oceans, the geographic distrution of earthquakes and volcanoes, the age of the sea floor

Question 24

earthquakes that occur near coastal areas can be very destructive because

Answer 24

liquifaction can occur, tsunamis can occur, water saturated sediments amplify seismic waves

Question 25

tsunamis occur when

Answer 25

earthquakes occur on the ocean floor

Question 26

stratovolcanoes form at

Answer 26

convergent plate boundaries

Question 27

geologically speaking a mountain is where the

Answer 27

crust is thicker

Question 28

the geologic time scale is

Answer 28

a calender of earth history, hierarchal, combines the two frameworks of geologic time

Question 29

geologists know that volcano is about to erupt if

Answer 29

the shape of the mountain changes, composition of gasses coming from volcano changes, there are numerous small earthquakes

Question 30

most mid ocean ridges (ocean ocean divergent plates boundaries) begin as

Answer 30

continent continet divergent plate boundaries, continental rifts

Question 31

what are some examples of the modern evidence for plate tectonics, and how is it different from continental drift?

Answer 31

earth quakes, volcanoes, | plate tectonics happen because of sea floor spreading, contentiental drift does not.

Question 32

what is the driving force for a volcanic eruption, and why are some volcanic eruptions more explosive than others

Answer 32

driving force is gasses building up | they are more explosive becuase of the silica in the magma it determines the viscosity

Question 33

what was not typical about the May 18, 1980 eruption of Mount St. Helen? what were some of the warning signs that this mountain was about to erupt?

Answer 33

the mountain blew out the side, warning signs were the change in the weather, it got all dark in the sky

Question 34

why was Wegener's idea of the continental drift rejected,and what was some of the evidence that he had that the continets had drifted into their present position?

Answer 34

it was rejected because floating continets, movement by centufugal force, aninadwquate mechanism. evidence- jigsaw fit of the continet's edge, paleoclimate indicators at wrong latitudes, glacial deposits (till and striations)