Geology Test 2 Flashcards
What is a seamount?
A volcano that forms on ocean floor
What is a continental shelf?
A gently sloping, submerged surface extending from the shoreline toward the deep ocean
What meteorologist proposed pangea?
Alfred Wegner
What was some of the evidence for Pangea?
- Fossils matching across the seas
- Continents fit together like jigsaw puzzles
- ## Rock types match on the edges of continents
Why did people object Wegner’s theory?
He had no mechanism for continental drift
What is the theory of plate tectonics?
Earth’s outer shell is made of fragmented, individual plates that interact in various ways & produce volcanoes and earthquakes
Whats the relationship between asthenosphere and lithosphere?
A rigid lithosphere overlies the weak asthenosphere
List all the plates
Major: North American, South American, Pacific, African, Eurasian, Australian-Indian, and Antarctic plate
Intermediate: North American, South American, Pacific, African, Eurasian, Australian-Indian, and Antarctic plate
Describe divergent plates
Where plates move apart, creating partial upwelling of material from the mantle and new seafloor. Located at oceanic ridges
Describe convergent plates
Where plates move together, resulting in either oceanic lithosphere descending beneath an overriding plate, then getting reabsorbed into the mantle, or in the collision of two continental blocks to create a mountain belt
Describe transform plates
Where two plates grind past each other without the production or destruction of lithosphere, least common
What is a rift valley?
A long trough that shows where divergence is taking place, there is one in Ireland
Describe continental rifting
Tensional movements that pull the lithosphere apart, the mantle upwells and makes the lith thin. The stretching makes the crust break into pieces that sink. That is the continental rift. Continued spreading creates a linear sea then a deep ocean basin.
What is a subduction zone?
Where the lithosphere subducts into the mantle, at convergent plates
The younger the seafloor, the more/less dense?
Young seafloor is less dense
what happens at an oceanic-continental convergence
They collide, oceanic subducts bringing water down with it, starting partial melting which produces magma. the magma rises and becomes a chain of erupting volcanos
what happens at an oceanic-oceanic convergence?
The older, denser of the two will subduct, Melting occurs and the magma rises and makes a volcanic island arc
what happens at a continental-continental convergence?
the two sides crunch into each other and huuuge mountains like the himalayas
What is some evidence that the plates are spreading?
They drilled into the ocean floor to check its age and depth of it, and near the rift the floor was thin and away from it was thick. AND volcanic chains like Hawaii show that volcanos are made in chains. Paleomagnetism.
