Introduction to the Geosphere Flashcards Preview

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Flashcards in Introduction to the Geosphere Deck (39):
1

Define the geosphere

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

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?

Variation in density and thickness between oceanic and continental crust

3

Composition of the continental crust

granitic on average, with feldspar and lighter elements; felsic

4

Composition of the oceanic crust

Maific, rich in Mg and Fe, not in silica

5

What was the Challenger

First scientific analysis of Deep Sea

6

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

260Ma

7

Why was continental drift hypothesized

The same fossils and land forms were found on different continents

8

Who proposed continental drift

alfred wagner

9

Who revamped the continental drift theory in the 60x

Arthur stahler

10

What was the alternative theory to continental drift

land bridges

11

Who hypothesized land bridges

Eduard Seuss

12

What is the formula used by SONAR

V = 2d/t

13

What does SONAR stand for

SOund Navigation and Ranging

14

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

Magnetometers

15

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

Heezen and Tharp in 1957
they produced the first publicly accesble map of the ocean floor

16

Who hypothesized that the earth was layered

Andrija Mohoveric

17

Who hypothesized that the outer core was liquid

Inge Lehman

18

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

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

19

What do the magnetic anomalies around oceanic ridges show

That the earth occasionally switches it poles

20

What generates the lithosphere

Generated by volcanism at mid oceanic ridges

21

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

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

22

Why are there continents

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

23

Why are land and oceanic plates of different composition

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

24

Why are there mountain belts

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

25

What is the subduction zone

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

26

How hawaii exists

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

27

Why is the oceanic crust so young?

Sediment keeps getting recycled into the mantle

28

Why are oceans shallower in the middle

thermal subsidence (definition on another slide on this deck)

29

define thermal subsidence

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

30

Where are plates generated at

Mid oceanic ridges

31

What is the composition of the mantle

ultramafic

32

Define viscoelestic

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

33

Where are plates returned to the mantle

Subduction zones

34

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

Collision of continental crust with continental crust

35

Why is continental crust so old relative to oceanic crust?

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

36

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

Partial melting

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

e

38

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

The main reason was lack of a viable mechanism.

39

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

thermal subsidence