Scientists
Collected sonar data from ships all over the world. In 1952, discovered the Mid- Atlantic Ridge, a 10,000 mile long water mountain range.
Marie Tharp
____________ creates new oceanic crust at mid ocean ridges.
The basalt nearest mid-ocean ridges is newer than the basalt that is farthest away. Because the oceanic crust is always being recycled, most oceanic crust is 200 million years old. (Remember, the Earth is 4.5 billion years old)
Age of Oceanic Crust
Who wrote the paper "The History of Ocean Basin"?
Harry Hess
Where subduction takes place.
trench
Collected sonar data using the Navy's depth sounder equipment during WW2. Credited with the theory of "seafloor spreading"
Harry Hess
__________ destroys old oceanic crust at trenches.
Subduction
Every 200,000 to 300,000 years, the Earth’s magnetic poles switch. We don’t know why. The Earth doesn’t geographically change, but a compass would point south instead of north.
When basalt, which contains iron oxide, flows out of mid-ocean ridges, it maintains a magnetic signature. Scientists can track the magnetic “stripes” on the ocean floor.
Magnetic Reversal
Happens during subduction?
The ocean crust sinks below the mantle
Crust where the ocean is located
oceanic crust
Was a flight instructor in the Army. In 1961, wrote a paper about seafloor spreading. Supporter of new and progressive scientific ideas. Tried to take credit for "seafloor spreading"
The idea that continents are slowly moving.
continental drift
Because of basalt’s properties, scientists can tell that the molten material was very hot when it erupted from the mid-ocean ridge. The formation, location, and age of the molten material at mid-ocean ridges show that new oceanic crust is being formed and pushing outwards to move the continents.
Molten Material
People used to think the seafloor looked like?
Flat with sediments from the continents
Crust where the land is located.
Continental Crust
Worked with Marie Tharp at Columbia University to map the ocean floor.
Bruce Heezen
A process where oceanic crust sinks down into the mantel. Old seafloor is destroyed.
subduction
Because basalt is constantly being pushed out at mid-ocean ridges, it forms undersea mountain ranges. The tallest parts of the ocean floor are mid-ocean ridges
Elevation of Ocean Floor
Pushes up from the Earth's mantle through a mid ocean mountains.
magma
Type of technology uses sound waves to "see" underwater.
sonar
Alfred Wegener
New, young, volcanic rock from mid ocean ridges. It is also called "pillow rock".
Basalt
Mid-ocean ridges are constantly pushing out molten material. This makes the temperature much hotter than in other parts of the ocean.
Water Temperature
10,000 mile underwater mountain range that Marie Tharp discovered.
Mid-Atlantic Ridge
Why is basalt a good indicator of magnetic stripes evidence of seafloor spreading?
It has magnetic properties.