Introduction to the Geosphere

Question 1

Define the geosphere

Answer 1

Dense, primarily solid part of the earth that consists of rocks and overlaying sediment

Question 2

The elevation of the Earth’s surface has a bimodal distribution, with one peak associated
with the continents, the other associated with the ocean floor. What explains this?

Answer 2

Variation in density and thickness between oceanic and continental crust

Question 3

Composition of the continental crust

Answer 3

granitic on average, with feldspar and lighter elements; felsic

Question 4

Composition of the oceanic crust

Answer 4

Maific, rich in Mg and Fe, not in silica

Question 5

What was the Challenger

Answer 5

First scientific analysis of Deep Sea

Question 6

If we look at the amount of sediment on the ocean floor, how old would the earth be, at present rates

Answer 6

260Ma

Question 7

Why was continental drift hypothesized

Answer 7

The same fossils and land forms were found on different continents

Question 8

Who proposed continental drift

Answer 8

alfred wagner

Question 9

Who revamped the continental drift theory in the 60x

Answer 9

Arthur stahler

Question 10

What was the alternative theory to continental drift

Answer 10

land bridges

Question 11

Who hypothesized land bridges

Answer 11

Eduard Seuss

Question 12

What is the formula used by SONAR

Answer 12

V = 2d/t

Question 13

What does SONAR stand for

Answer 13

SOund Navigation and Ranging

Question 14

What other instrument besides sonar was used to map the surface of the ocean

Answer 14

Magnetometers

Question 15

Who did the first expedition using sonar to map the bottom of the ocean, and what was the result

Answer 15

Heezen and Tharp in 1957

they produced the first publicly accesble map of the ocean floor

Question 16

Who hypothesized that the earth was layered

Answer 16

Andrija Mohoveric

Question 17

Who hypothesized that the outer core was liquid

Answer 17

Inge Lehman

Question 18

What three things characterize the mid oceanic ridges (apart from the fact they are ridges)

Answer 18

1. Characterized by high heat flow
2. seidment thickness and age increased as you move further away
3. opposite dipole strips move like a bar code away from them

Question 19

What do the magnetic anomalies around oceanic ridges show

Answer 19

That the earth occasionally switches it poles

Question 20

What generates the lithosphere

Answer 20

Generated by volcanism at mid oceanic ridges

Question 21

How are the plates recycled, and what are these places called

Answer 21

One pushes underneath another plate, getting absorbed into the mantle. Called subduction zones

Question 22

Why are there continents

Answer 22

They are composed of lighter material and float on top of the mantle like an iceberg

Question 23

Why are land and oceanic plates of different composition

Answer 23

The oceanic plates are made from uniformly melted mantle that has a more uniform chemistry. Land plates are made of many different cycles of partial melting, and are not uniform

Question 24

Why are there mountain belts

Answer 24

continents crashing into each other, or by large scale volcainc eruption

Question 25

What is the subduction zone

Answer 25

where one plate goes under another, and gets absorbed into the mantle

Question 26

How hawaii exists

Answer 26

It is a mid plate plume of magma
Does not move, the mantle jsut moves over top
It is a hot spot

Question 27

Why is the oceanic crust so young?

Answer 27

Sediment keeps getting recycled into the mantle

Question 28

Why are oceans shallower in the middle

Answer 28

thermal subsidence (definition on another slide on this deck)

Question 29

define thermal subsidence

Answer 29

The oceanic lithosphere becomes thicker and denser as it cools. therfore, the middle of the ocean will be thickest, because it is the coldest

Question 30

Where are plates generated at

Answer 30

Mid oceanic ridges

Question 31

What is the composition of the mantle

Answer 31

ultramafic

Question 32

Define viscoelestic

Answer 32

Having both the properties of a solid and a liquid (the mantle is like this)

Question 33

Where are plates returned to the mantle

Answer 33

Subduction zones

Question 34

What explains mountain belts that reside in the interior of continents (e.g., Himalayas)?

Answer 34

Collision of continental crust with continental crust

Question 35

Why is continental crust so old relative to oceanic crust?

Answer 35

Oceanic crust is continuously being recycled into the mantle at subduction zones, whereas
continental crust is too buoyant to undergo this process

Question 36

What explains the compositional difference between continental crust, oceanic crust, and
the mantle?

Answer 36

Partial melting

Question 37

Which of the following observations did Alfred Wegener use to support his continental drift
hypothesis?
a) The observation that the mid-oceanic ridge is a long, linear volcano
b) The observation that oceanic crust has a barcode-like magnetic signature
c) The observation that the age of oceanic crust increases away from spreading ridges
d) The observation that the age of basal sediments overlying the oceanic crust increases
away from spreading ridges
e) None of the above

Answer 37

e

Question 38

Why was Wegener’s continental drift hypothesis rejected when he proposed it initially?

Answer 38

The main reason was lack of a viable mechanism.

Question 39

Why does the ocean floor increase in depth from mid oceanic ridges towards the adjacent
continents?

Answer 39

thermal subsidence