13.2- Seafloor Spreading

Question 1

When did people discover the ocean wasn’t flat

Answer 1

Mid 1900s

Question 2

What allowed scientists to study the ocean floor in great detail

Answer 2

echo sounding methods

Question 3

Mid Ocean Ridge

Answer 3

chain of underwater mountains that run throughout the ocean basins
form the longest continuous mountain range on Earth
Total length of 65,000 km
Up to 3 km above the ocean floor

Question 4

____________ and ____________ are common amung ocean ridges

Answer 4

Earthquakes and volcanism

Question 5

Deep Sea Trench

Answer 5

a narrow, elongated depression in the seafloor
can be thousands of km long and deep

Question 5

what is the deepest trench?

Answer 5

mariana trench
11 km deep

Question 5

The age of oceanic crust consistently ______________ with ________________ from a ridge

Answer 5

increases, distance

Question 5

Rocks closer to ocean ridges are what

Answer 5

younger

Question 5

Rocks farther away from ocean ridges are what

Answer 5

older

Question 5

Ocean floor sediments are typically how thick

Answer 5

few hundred meters

Question 6

The oldest rocks on the ocean floor are how old

Answer 6

180 million years old

Question 6

The _______________ of the sediments ________________ with _____________ from an ocean ridge

Answer 6

thickness, increases, distance

Question 6

Large areas of continents have ____________________ that are up to ____________ thick

Answer 6

sed rocks, 20 km

Question 7

What causes a compass needle to point north

Answer 7

Earth’s magnetic field generated by the flow of molten iron

Question 8

Magnetic Reversal

Answer 8

when Earth’s magnetic field changes polarity between normal and reversed
has occurred many times

Question 9

Paleomagnetism

Answer 9

study if the history of earth’s magnetic field

Question 10

When lava solidifies what crystallizes

Answer 10

iron-bearing minerals
they behave like mini compasses and align with earth’s magnetic field

Question 11

regions of ________________ and ________________ form a series of stripes along the ________________ parallel to ____________________

Answer 11

normal, reverse polarity, floor, ocean ridges

Question 12

Isochron

Answer 12

an imaginary line on a map that shows points that have the same age

Question 13

Seafloor Spreading

Answer 13

the theory that explains how new oceanic crust is formed at mid ocean ridges and destroyed at deep sea trenches

Question 14

What verified Wegeners theory of continental drift

Answer 14

seafloor spreading