During sea-floor spreading, oceanic crust forms at the mid-ocean ridge. This crust gradually moves toward
a subduction zone
, where old crust sinks beneath a trench. As sea-floor spreading occurs, old oceanic plates sink into the mantle in the process of subduction. Subduction zones are near the edges of oceanic plates.
Where does the old crust go?
The farer away from the ridge the ocean crust is the older the crust is. The oldest crust is
at edges of the ocean
. One place where the crust is the oldest is at edge of a subduction zone. It is here that the oldest ocean crust is pushed under a continental crust and destroyed.
Where does the old crust move when the seafloor spreads quizlet?
The older rock moves
outward on both sides of the ridge
as new rock forms in the center of the ridge from cooling of molten material. This process is sea floor spreading.
How does seafloor spreading move plates quizlet?
Divergent
boundaries
create rift valleys at the continents while they create seafloor spread on the ocean. The tectonic plates in this boundary move apart from each other. … The more dense ocean plate subducts under the continental plate.
What is the oldest crust on Earth?
Earth’s oldest known piece of continental crust dates to the era of the moon’s formation.
Australia
holds the oldest continental crust on Earth, researchers have confirmed, hills some 4.4 billion years old.
What is the age of the oldest oceanic crust found on Earth?
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.
What are 2 pieces of evidence that support 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.
What is the root 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. Eventually, the crust cracks.
What happens when a piece of crust is subducted?
Where two tectonic plates meet at a subduction zone,
one bends and slides underneath the other, curving down into the mantle
. (The mantle is the hotter layer under the crust.) … At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust.
What are the steps in 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.
Which two boundaries are associated with areas of seafloor spreading?
Sea-floor spreading is what happens at the mid-oceanic ridge where
a divergent boundary
is causing two plates to move away from one another resulting in spreading of the sea floor. As the plates move apart, new material wells up and cools onto the edge of the plates.
What is caused by the crust movement?
Earth’s crust, called the lithosphere, consists of 15 to 20 moving tectonic plates. …
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.
What is the youngest ocean?
The Atlantic Ocean
is the world’s saltiest sea with a water salinity level of between 33 – 37 parts per thousand. It’s the world’s youngest ocean, formed long after the Pacific, Indian and Arctic Oceans of the Triassic Period.
Where is oceanic crust thickest?
Crust is thickest where
there are mountains
, so the Moho will be deeper under mountains than under the oceanic crust. Since oceanic crust is also denser than continental crust, it floats lower on the mantle.
Where would the oldest rocks on Earth be found?
That’s right, geologists,
Canada
is home to the world’s oldest discovered rocks! When the Earth was formed about 4.6 billion years ago, the molten rock on the surface hardened to form a solid crust.
Where is the youngest seafloor found?
Where plates move apart, new crustal material is formed from molten magma from below the Earth’s surface. Because of this, the youngest sea floor can be found
along divergent boundaries, such as the Mid-Atlantic Ocean Ridge
.
