What evidence did Alfred use?
He used fossil evidence, such as that of tropical plants found on the Arctic island of Spitzbergen. He found large-scale geographic features that matched, like the Appalachian Mountains in the United States and the Scottish Highlands, as well as rock strata in South Africa that matched those in Brazil.
What are the evidence of seafloor spreading?
Abundant evidence supports the major contentions of the seafloor-spreading theory. First, samples of the deep ocean floor show that basaltic oceanic crust and overlying sediment become progressively younger as the mid-ocean ridge is approached, and the sediment cover is thinner near the ridge.
What are 3 pieces of evidence for the theory of seafloor spreading?
Look at Figure 19 to see the process of sea-floor spreading. Several types of evidence from the oceans supported Hess’s theory of sea-floor spreading-evidence from molten material, magnetic stripes, and drilling samples. This evidence also led sci- entists to look again at Wegener’s theory of continental drift.
What are the three types of seafloor spreading?
There are three types of plate-plate interactions based upon relative motion: convergent, where plates collide, divergent, where plates separate, and transform motion, where plates simply slide past each other.
What are the features of seafloor?
Features of the ocean include the continental shelf, slope, and rise. The ocean floor is called the abyssal plain. Below the ocean floor, there are a few small deeper areas called ocean trenches. Features rising up from the ocean floor include seamounts, volcanic islands and the mid-oceanic ridges and rises.
What part of the ocean is 5200 m?
Tasman Basin
What is the seafloor called?
seabeds
What is the seafloor made of?
Oceanic crust is about 6 km (4 miles) thick. It is composed of several layers, not including the overlying sediment. The topmost layer, about 500 metres (1,650 feet) thick, includes lavas made of basalt (that is, rock material consisting largely of plagioclase [feldspar] and pyroxene).
How is seafloor destroyed?
Framework Integration: Themes: Patterns of change: over time, new sea-floor is created by the upwelling of magma at mid-ocean spreading centers; old ocean floor is destroyed by subduction at deep sea trenches. Life Science: animals found at hot-water vents on the ocean floor.
At what 2 types of boundaries are trenches created?
In particular, ocean trenches are a feature of convergent plate boundaries, where two or more tectonic plates meet. At many convergent plate boundaries, dense lithosphere melts or slides beneath less-dense lithosphere in a process called subduction, creating a trench.
Where is seafloor destroyed?
You are correct that the seafloor is destroyed at subduction zones, but it is simultaneously being created at mid-ocean ridges. see figure 1 . Figure 1: Seafloor spreading at a mid-ocean ridge(where new crust is being created) and it’s destruction at a subduction zone.
Is seafloor destroyed?
The seafloor is destroyed at a COnvergent Boundary. You will find the oldest seafloor at a COnvergent Boundary. There will be a trench, not a ridge.
What do the side slits represent?
The side slits stand for where subduction has occurred and the ocean floor has sunk in. Also, the space under the paper stands for the oceanic crust of the Earth.
What is the cause of seafloor spreading?
Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor.
What are the 4 steps of seafloor spreading?
What are the 4 steps of seafloor spreading?
- Magma comes out of the rift valley.
- Magma cools to rock and hardens.
- Rock is pushed away as new rock is formed at MOR.
- Oceanic crust and continental crust meet at the trench.
- Oceanic crust bends down under the continental crust.
- Gravity pulls rock towards mantle.
- Rock melts to mantle.
What causes the Earth’s crustal plates to move?
The heat from radioactive processes within the planet’s interior causes the plates to move, sometimes toward and sometimes away from each other. This movement is called plate motion, or tectonic shift.
Who discovered seafloor spreading?
Harry Hess
How old is the seafloor?
150 million years
What is the first step of seafloor spreading?
A crack forms in oceanic crust. Molten rock rises up through oceanic crust. Molten rock solidifies at the center of the ridge.
Why is the earth not getting bigger or smaller?
New crust is continually being pushed away from divergent boundaries (where sea-floor spreading occurs), increasing Earth’s surface. But the Earth isn’t getting any bigger. Deep below the Earth’s surface, subduction causes partial melting of both the ocean crust and mantle as they slide past one another.