Chapter 2: Plate Tectonics Slide Set 6 Flashcards
Who is Marie Tharp?
was an American geologist and oceanographic cartographer who, in partnership with Bruce Heezen, created the first scientific map of the Atlantic Ocean floor. Tharp’s work revealed the presence of the Mid-Atlantic Ridge, causing a paradigm shift in earth science that led to acceptance of the theories of plate tectonics and continental drift.
How does continental lithosphere break apart?
- Lithosphere stretches and thins.
- Brittle upper crust faults.
- Ductile lower crust flows.
- Asthenosphere rises and melts.
- Magma erupts.
What happens when the lithosphere if it keeps breaking?
- Continuation can create a new mid-ocean ridge.
- This process led to the breakup of Pangaea.
The continental rifting arises from _____
tensional forces that break the crust along a complex jumble of normal faults.
Explain how did The Colorado Plateau developed
- Western U.S. Basin and Range Province is a rift.
- Narrow north-south mountains separated by basins.
- Rifting tilted blocks of crust to form mountains.
- Sediment eroded from blocks, filling adjacent basins
Explain the early stage of Divergent Boundaries
- Rifting has progressed to mid-ocean ridge formation.
- Before substantial widening of the ocean.
- Forms a long, thin ocean basin with young oceanic crust
Give an example of an early stage divergent boundary
The Red Sea
Explain the East African Rift
- The Arabian plate is rifting from the African plate.
- Rifting has progressed to sea-floor spreading in:
- The Red Sea.
- The Gulf of Aden.
- Stretching continues along the East African Rift.
- Elongate trough bordered by faulted high cliff
- Volcanoes – Mt. Kilimanjaro
- The rift and two spreading ridges comprise a triple junction.
Explain the mid stage of Divergent Boundaries
- Ocean begins to widen.
- New sea-floor is added at the mid-ocean ridge.
- Continents move farther apart.
Give an example of an mid stage divergent boundary
Greenland and the North Atlantic
Explain the late stage of Divergent Boundaries
- Mature, wide ocean basin.
- Linear increase in age with distance from central ridge.
- Edge of ocean basin—oldest; ridge proximal—youngest
Give an example of an late stage divergent boundary
The Atlantic Ocean
The hot asthenosphere is at the base of the ___
mid-ocean ridges
What happens to the aging ocean crust?
Aging ocean crust moves away from this heat source:
- Cooling, increasing in density and sinking.
- Older, thicker lithosphere sinks deeper into mantle.
How did the Red Sea form?
- Rifting has progressed to mid-ocean ridge formation.
- Before substantial widening of the ocean.
- Forms a long, thin ocean basin with young oceanic crust.
The Red Sea and the Gulf of Aden were formed as the Arabian plate separated from Nubia, as Nubia obliquely collided with the Eurasian plate
Using concepts from Plate Tectonics, explain how the Red Sea formed.
A clear example of continental rifting is found in the Rift Valley in East Africa. As you can see on the map on the left, the continental rift is at a divergent plate boundary. When the plates move apart, magma rises up through the fractures as lava, pushing the continental lithosphere on either side further apart. If the process of rifting continues, this continent will end up splitting in two.
This is what has happened in the Red Sea. The Red Sea Rift separates the Arabian Peninsula from Africa. It once was a continental rift, but now it is an oceanic rift, generating oceanic lithosphere.
Where is the youngest ocean floor located?
Youngest rock on the ocean floor can be seen in divergent plate boundaries and hot spots.
Where is the oldest ocean floor located?
It is found in the Mediterranean Sea and is a remnant of an ancient ocean that is disappearing between Africa and Europe.
