Ch. 1 sec 4-5 Sea Floor Spreading Flashcards
What did sonar help accomplish?
It helped discover that the ocean floor isn’t flat but has mountains and valleys and discovered the mid ocean ridges
Sonar-
Used to map the ocean floor.
What did Harry Hess do?
He studied mid oceanic ridges and came up with “sea floor spreading”
What’s sea floor spreading?
A theory which states that molten material comes up through cracks at mid ocean ridge, it hardens and spreads the sea floor by pushing older rock away.
What theory backed up continental drift?
Sea floor spreading
What is an evidence from molten material?
The sea floor near the mid oceanic ridge is volcanic
What’s and evidence from magnetic stripes?
- Earth has changed polarity several times and it’s recorded in the ocean.
- The magnetic stripes are the same distance from the mid ocean ridges showing that the ocean floor was made at the same time and the sea floor has spread.
Evidence from the age of the rock drilling samples
- Scientists drill rock samples and find the age of the rock is the same distance from the mi ocean ridge, showing that the rock was ,made at the same time. and was split apart by Sea Floor Spreading.
Subduction
The process where ocean floor runs into ocean floor or ocean floor runs into continental crust and ocean floor sinks down forming a trench.
What happens when two oceanic crusts collide?
Islands
Ocean crust collides with Continental crust
Trenches
Continental crust collides with Continental crust
mountains
The subduction zone
the whole area where subduction
Plates-
Parts of the lithosphere that is broken off
Plate tectonics-
A geological that states that pieces of Earth’s lithosphere are moving in constant slow motion, driven by convection currents in the mantle.
What makes Earth’s plates move?
Convections currents rise from the asthenosphere and spread out beneath the lithosphere
What are the edges of the plates called?
Plate boundaries
Transform boundaries-
A place where 2 boundaries are sliding past each other. Causing earth quakes.
Divergent boundary
Where two plates move apart
What happens to divergent boundaries on land?
Rift valleys
Rift Valley
a deep valley that forms where two plates move apart
What happens when divergent boundaries occur in the ocean?
it causes mid-ocean ridges
Convergent boundary
Where two plate boundaries collide and it causes mountains
Faults
Breaks in the earths crust where rocks slipped past each other
