Ocean Floor Flashcards
(59 cards)
Pangea
the theory that there was just one land mass
Theory of Plate tectonics
theory that suggests that the outer crust of the Earth, known as the lithosphere, consists of a number of separate plates which ‘float’ on the underlying layer (the mantle)
Convergent boundaries
where two plates are moving toward each other
Divergent boundaries
where two plates are moving away from each other and new crust is forming from magma that rises to the Earth’s surface between the two plates
Transform boundaries
where plates slide sideways past each other
Evidence supporting the theory of plate tectonics includes:
- fits between continents (for example the east coast of South America and the west coast of Africa);
- paleontology showing the distribution of fossil species;
-magnetic stripes in the ocean floor.
The pattern of magnetic stripes provides clear evidence of ocean floor spreading
Lithosphere
the rigid outer part of the earth, consisting of the crust and upper mantle
Subduction
(where one plate is forced under another)
the sideways and downward movement of the edge of a plate of the earth’s crust into the mantle beneath another plate
Ocean trenches are…
long and narrow and are the deepest part of the ocean floor
Mid-ocean ridges are…
underwater mountain ranges, formed by upward movement and cooling of the underlying magma, which cools and solidifies as it emerges
Mountain range formation occurs at…
divergent tectonic plate boundary and is responsible for seafloor spreading
Abyssal plains
relatively flat areas of the ocean floor, situated between ocean ridges and continental rises
Mantle convection (process of abyssal plain being formed)
the upwards movement of molten material from the oceanic crust, which solidifies and forms new ocean crust.
How is a volcano formed
where there is an opening in the Earth’s crust, allowing hot gases and molten rock to escape from below the surface
Volcanoes can be formed…
where tectonic plates are moving towards each other (convergent)
Earthquakes occur when…
there is a sudden release of energy in the Earth’s crust, creating shock waves
What happens when two plates slip past eachother?
they may lock. Continued plate movement results in strain building up until the plates suddenly move again, release stored energy and creating an earthquake
Tsunami
a very large wave produced by the sudden movement of a very large volume of water
Process of tsunami development
In deep, oceanic water, a tsunami wave travels quickly. As the wave approaches shallow, coastal water, it slows down but forms large, waves
Hydrothermal vents occur…
in the deep ocean, typically along mid-ocean ridges where two tectonic plates are diverging
How are hydrothermal vents formed?
- Sea water which seeps into cracks in the ocean floor and water from the upwelling magma, is released from the hot magma
- A hydrothermal vent forms where the hot water passes up through the ocean floor and, as it cools, the dissolved minerals start to precipitate out.
Minerals in a hydrothermal vent include…
the sulphide of iron, copper and zinc.
Hrydrothermal vents can be super heated when…
There is high pressure
Isostasy
the buoyant properties of layers of rocks which floats on other layers, according to their density and thickness
