Subduction
is the process by which the ocean floor sinks beneath a deep-ocean trench
What happens to the old seafloor as it is pushed into the mantle?
When the seafloor subducts it does disappear from the surface
. It moves deeper into the Earth, into the mantle. But in the Pacific ocean there are also ridges, called spreading centers, where new seafloor is created.
When oceanic crust sinks back into the mantle it sinks through?
At deep-ocean trenches,
subduction
allows part of the ocean floor to sink back into the mantle, over tens of millions of years. The processes of subduction and sea-floor spreading can change the size and shape of the oceans. Because of these processes, the ocean floor is renewed about every 200 million years.
What happens to the old oceanic crust as new molten material rises from the mantle?
A ridge forms along a crack in the oceanic crust.
At a mid-ocean ridge
, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge. … This process, called sea-floor spreading, continually adds new material to the ocean floor.
What will happen to the old oceanic crust materials?
Oceanic crust slowly moves away from mid-ocean ridges and sites of seafloor spreading. As it moves, it becomes cooler, more dense, and more thick. Eventually, older
oceanic crust encounters a tectonic boundary with continental crust
.
Where 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
.
What are two pieces of evidence for seafloor 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.
Where is the seafloor spreading the fastest?
Some of our recent research involves hydrothermal and structural investigations along Earth’s fastest seafloor spreading center, the 28°S–32°S East Pacific Rise. The fastest present-day seafloor spreading, ~150 km/Myr, occurs
along the Pacific-Nazca boundary between the Easter and Juan Fernandez microplates
.
What do you call it when the oceanic crust bends downward?
A subduction zone
is the biggest crash scene on Earth. … At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust. (Sometimes, oceanic crust may grow so old and that dense that it collapses and spontaneously forms a subduction zone, scientists think.)
Is a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle?
deep ocean trench
– a deep valley along the ocean floor through which oceanic crust slowly sink toward the mantle.
What happens when two plates carrying continental crust collide?
Plates Collide When two plates carrying continents collide, the continental crust buckles and rocks pile up,
creating towering mountain ranges
. The Himalayas were born when the Indian subcontinent smashed into Asia 45 million years ago.
Where is oceanic crust the thickest?
The crust is thickest
under high mountains
and thinnest beneath the ocean.
Where is the oldest oceanic crust found?
The oldest patch of undisturbed oceanic crust on Earth may lie
deep beneath the eastern Mediterranean Sea
– and at about 340 million years old, it beats the previous record by more than 100 million years.
Why is older oceanic crust denser?
It is due to the process of subduction; oceanic crust tends to
get colder and denser with age
as it spreads off the mid-ocean ridges. It gets so dense, that it sinks in the upper mantle (subduction). This is like a giant recycling system for the oceanic lithosphere.
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 boundaries is seafloor destroyed?
At
convergent plate boundaries
, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed.
