Plate tectonics

Question 1

Plate tectonics:

Answer 1

is a theory addressing the origin, movement, and recycling of lithospheric plates and the resulting landforms.

• Lithosphere is broken into 14 major and minor plates that move over Earth’s surface as mantle beneath them convects.

Question 2

how do earthquakes occur?

Answer 2

As the plates move they buckle, bend, and warp into mountains, split into valleys, and break, causing earthquakes

Question 3

Continental drift:

Answer 3

a theory that proposed continents move slowly across Earth’s surface.

• Proposed in 1912 by Alfred Wegener

Question 4

how did Alfred wegener come up with continental drift theory?

Answer 4

he noticed jigsaw-puzzle fit between east coast of South America and west coast of Africa

and he used evidence from matching rock types on separated continents, deposits of glacial gravels, and fossils of organisms

Question 5

Pangaea:

Answer 5

“whole land”; a supercontinent that formed 300 million years ago

• Transition from Pangaea to today’s continents occurred in two major steps: opening of Tethys sea and opening of Atlantic Ocean
• Pangaea split into Laurasia and Gondwana about 200 million years ago

Question 6

Laurasia:

Answer 6

Laurasia: the landmasses that would become North America, Greenland, and Eurasia

Question 7

Gondwana:

Answer 7

the landmasses that would become South America, Australia, Africa, India, and Antarctica

Question 8

plate tectonics history

Answer 8

• After World War II, sonar provided new evidence that led to development of theory of plate tectonics
• In 1960, Hess formalized theory of seafloor spreading, which developed into broader theory of plate tectonics

Question 9

can plates recycle?

Answer 9

yes.

e.g. a new lithosphere forms at mid-ocean ridges, and old lithosphere is recycled deep into the mantle through subduction.

Question 10

subduction:

Answer 10

the process in which the oceanic lithosphere of one plate bends and dives into the mantle beneath another plate.

Question 11

plate boundaries:

Answer 11

is the places where lithospheric plates meet

• Fourteen plates
  
  • 7 primary and 7 secondary
  • Largest plate is Pacific Plate

Question 12

what are the 3 types of plate boundaries?

Answer 12

1) Divergent: Where two plates move apart.
2) Convergent: Where two plates move toward each other.
3)Transform: Where one plate slips laterally past another.

Question 13

the continental margins

Answer 13

Active continental margin: typically consists of deep-sea trench and narrow continental shelf.

Passive continental margin: typically has broad, sloping continental shelf and does not coincide with plate boundary.

Only some plate boundaries follow outlines of continents

Question 14

Ridge push:

Answer 14

kind of plate movement.

the process by which magma rising along a mid-ocean ridge lifts oceanic lithosphere and forms a slope

Question 15

Mantle drag:

Answer 15

kind of plate movement.

movement of a plate caused by friction between moving asthenosphere and the lithosphere

Question 16

Slab pull:

Answer 16

the weight of the subducting portion of a plate (a slab) accelerates plate movement by pulling the plate deeper into the mantle

Question 17

2 kinds of plate velocity

Answer 17

Absolute velocity: how fast the plate moves in relation to a fixed point, such as the center of the Earth.

Relative velocity: how fast a plate moves in relation to the speed of an adjacent moving plate.

Fastest relative velocity plate movement is 18 cm (7 in) per year.
Pacific and Nazca plates near Easter Island are fastest-moving plates