5/19 Plate Tectonics

Front 1

Layers of the Earth

Back 1

Crust, Lithosphere, Asthenosphere, Mantle, Outer Liquid Core, Inner Solid Core

Front 2

The averagethickness of the lithosphere isabout 75 kilometers beneath theoceans, but is about ___ kilometers beneath continents.

Back 2

125

Front 3

In the early 20th century, the youngGerman scientist ________ __________, notedthat the African and South Americancoastlines appear to fit together likeadjacent pieces of a jigsaw puzzle.

Back 3

Alfred Wegener

Front 4

Geographic distributions of plant and animal fossils on Wegener’s map indicate that asingle super continent, called _______, existed from about 300 to 200 million years ago.

Back 4

Pangea

Front 5

Shortly after WWII, scientists began to explore the floors of the Earth’soceans. As they mapped the sea floor, oceanographers discovered thelargest mountain chain on Earth, now called the. . .

Back 5

Mid-Oceanic Ridge system

Front 6

Currently, the north magnetic pole is located near Earth's North Pole, a condition called...

Back 6

normal polarity.

Front 7

Periods when the north magnetic pole is located near Earth's South Pole are called...

Back 7

reversed polarity.

Front 8

When molten lava solidifies at mid-ocean ridges, iron-containing minerals in the lava align themselves with Earth's active ________ _______. These minerals record the orientation of the _______ _______ at the time they solidified.

Back 8

magnetic field

Front 9

The __________ is a shell of hard, strong rock about 100 km thick that floats on the hot, plastic ___________.

Back 9

lithosphere, asthenosphere

Front 10

The lithosphere is broken into seven large (and several smaller) segments called ________ _______.

Back 10

tectonic plates

Front 11

The tectonic plates glide slowly over the asthenosphere at rates ranging from less that 1 to about 16 __ per year

Back 11

cm

Front 12

The mantle and lithosphere circulate in huge ________ _______ that rise from the deepest mantle, then flow across the Earth’s surface, and finally sink back to the mantle-core boundary.

Back 12

elliptical cells

Front 13

At a ________ _______ _________, rocks on opposite sides of the fracture slide horizontally past each other.

Back 13

transform plate boundary

Front 14

Two plates come together at a ________ boundary.

Back 14

convergent

Front 15

Two plates separate at a ________ boundary.

Back 15

divergent

Front 16

New lithosphere at the oceanic spreading center is hot and therefore of ________ density.

Back 16

low

Front 17

The Afar Triangle is a so-called triple junction (or triple point), where three plates are pulling away from one another. These three are...

Back 17

the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somalian)

Front 18

Where two plates of different density converge, the denser one sinks into the _____ beneath the other. This sinking process is called...

Back 18

mantle, subduction

Front 19

A ______ _______ is a long, narrow belt where a lithospheric plate is sinking into the mantle

Back 19

subduction zone

Front 20

Plate convergence can occur...

Back 20

(1) between a plate carrying oceanic crust and another carrying continental crust,

(2) between two plates carrying oceanic crust, and

(3) between two plates carrying continental crust.

Front 21

When two oceanic plates converge, one is usually subducted under the other, and in the process a _____ is formed.

Back 21

trench

Front 22

The ______ Trench is the deepest part of the world's oceans, and the deepest location on the surface of the Earth's crust.

Back 22

Mariana

Front 23

The San Andreas fault system is an example of what kind of plate boundary

Back 23

transform plate boundary