Earth Science B Chapter 10

According to Wegener, how did continents move?

Continents plowed through rock on ocean floor (this was disproved)

What deep-ocean feature forms a subduction zones

Deep-ocean trenches

Oceanic crust

Dense crust made of rock that is rich in iron and magnesium

Slab pull

The force exerted buy a sinking plate caused by the subduction of lithosphere into the asthenosphere

Ridge pushing

The force on the rest of the plate from the asthenosphere below cooling sinking rock

rifting

The process by which a continent breaks apart

accretion

The process by which a terrane becomes part of a continent

Compared to sediment found farther from a ridge, sea-floor sediment closer to a ridge is

thinner

Compared to rocks farther from a ridge, rocks closer to a ridge are

younger

rift

A crack in Earths crust

Sea-floor spreading

A mechanism that causes the continents to move and verifies Wagener hypothesis of continental drift is

Rift valley

A narrow area that forms where the plates at a divergent boundary separate (i.e Red Sea)

terrane

A piece of lithosphere that has a unique geologic history

atoll

A small coral island

seamount

A small volcanic island of underwater mountain

earthquakes

A sudden movement along the boundary of a tectonic plate

Pacific Ring of Fire

A zone of active volcanoes and earthquakes the encircles the Pacific Ocean

How many major tectonic plates have scientists identified

About 15

Where does new rock form on the sea floor

At the rift in a mid-ocean ridge

Tectonic plates

Blocks of earths shell that ride on a deformable layer of the mantle

divergent

Boundary between tectonic plates that are moving away from each other

transform

Boundary between tectonic plates that are sliding past each other horizontally

How do Continents move over earths surface

By the widening sea floor, which acts as a conveyor belt

Island arc

Chain of volcanic islands

How are transform boundaries different from other types of boundaries

Don't produce magma (i.e San Andreas Fault)

Where were the older rocks on the sea floor

Farther away on either side of the ridge

Most of earths continental surfaces were once covered by

Ice (all continents were located near the south pole)

cratons

Large areas of stable rock older than 540 million years

Supercontinent

Large landmasses formed in the past from smaller continents

Continental crust

Low-density crust made of rock that is rich in silica

magma

Molten rock

Continental Drift

Movement of continents that are located on separate tectonic plates.

Supercontinent form when

New convergent boundaries form after continents collide

Rocks with magnetic fields that point north have

Normal polarity

subduction zone

Region where one plate moves under another

Rocks with magnetic fields that point south have

Reversed polarity

Scientists have found evidence of reversal patterns in

Rocks on the ocean floor and on land

shield

Rocks that have been exposed at earths surface

Fracture zone

Short segments of a mid-ocean ridge that are connected by transform boundaries

"plastic" rock

Solid rock under great pressure that flows slowly, like putty

asthenosphere

Solid, plastic layer of the mantle beneath the lithosphere

How do scientists identify plate boundaries

Studying data from earthquakes

What did Wegener hypothesize about mountain ranges ?

That the crumpling of the crust in places produced them

Pangaea

The Supercontinent that formed about 300 million years ago

The Tethys Sea

The body of water on the eastern edge of pangaea (eventually became the Mediterranean Sea)

convergent

The boundary between tectonic plates that are colliding

Where were the youngest rocks on the sea floor

The center of the ridge

Convection cell

The cycle in which the cooler, denser water sinks and the warmer water rises to the surface to create a cycle

lithosphere

The solid outer layer of earth, that consists of the crust and the rigid upper apart of the mantle

paleomagnetism

The study of the magnetic properties of rocks

Plate tectonics

The theory that explains why an how continents move

Fracture zones

Transform boundaries that connect short segments of a mid-ocean ridge

Mid-ocean ridge

Undersea mountain range

Mid-ocean ridges

Undersea mountain ranges with steep, narrow valleys in the center are called

Compared to speed of plates that are not subduction, plates that are subduction move

faster