Why does thickness of the oceanic lithosphere increase with distance from the ridges?
6. Why does thickness of the oceanic lithosphere increase with distance from the ridges? The temperature of the underlying mantle increases, decreasing its density, and therefore separates from the lithosphere.
Why is the lithosphere thicker in trenches?
The oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into the lithospheric mantle, and causes the oceanic lithosphere to become increasingly dense with age.
How does seafloor spreading affect the lithosphere?
The denser lithospheric material then melts back into the Earth's mantle. Seafloor spreading creates new crust. Subduction destroys old crust. The two forces roughly balance each other, so the shape and diameter of the Earth remain constant.
What is the result of the thickening with distance from the ridge?
In addition to becoming thicker with distance from the ridge axis, the lithospheric mantle becomes denser. This is an important factor in global tectonics, because after ∼10 Myr oceanic lithosphere is denser than the asthenospheric mantle and can therefore subduct into the mantle.
What processes explain the thickening of the lithosphere?
Thickening of lithospheric plates is best explained by understanding that: collision of continental plates pushes rocks of the same density together. The temperature of ocean rocks is coolest near midocean ridges and increases as rocks get closer to continental margins.
Where is oceanic lithosphere thickest and why?
The thickest oceanic lithosphere can be up to a hundred kilometers thick, where the upper mantle has cooled underneath a comparatively thin, old layer of oceanic crust. Continental lithosphere is thinnest where it overlies the very hot, viscous upper mantle at the thinnest fringes of active continental rifts.
Where is lithosphere thickest?
The thickest continental lithosphere consists of approximately 40 km of crust overlying 100 to 150 km of cold, but somewhat buoyant, upper mantle, and is found in continental cratons (interiors).
What causes the lithospheric plates to move?
The plates can be thought of like pieces of a cracked shell that rest on the hot, molten rock of Earth's mantle and fit snugly against one another. The heat from radioactive processes within the planet's interior causes the plates to move, sometimes toward and sometimes away from each other.
What happens when seafloor spreading occurs?
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 happens to the thickness of sediments further away from the ridge?
As you move away from the ridge spreading center the sediments get progressively thicker (see section 4.5), increasing by approximately 100-200 m of sediment for every 1000 km distance from the ridge axis.
What happens as a result of ridge push?
Ridge push is the result of gravitational forces acting on the young, raised oceanic lithosphere around mid-ocean ridges, causing it to slide down the similarly raised but weaker asthenosphere and push on lithospheric material farther from the ridges.
What processes explain the thickening of the lithosphere quizlet?
Thickening of lithospheric plates is best explained by understanding that: collision of continental plates pushes rocks of the same density together. The temperature of ocean rocks is coolest near midocean ridges and increases as rocks get closer to continental margins.
Is the lithosphere thicker near ridges or trenches?
Click below to visit our MapMaker Interactive layer displaying the lithosphere's tectonic plates. The lithosphere is thinnest at mid-ocean ridges, where tectonic plates are tearing apart from each other.
How are plates of the lithosphere moved *?
Explanation: Convection currents in the mantle cause the heating of Earth's plates and therefore, cause them to move. When warm material rises up, the cold material sinks down and this pattern repeats over and over. This causes the plates to rise and move.
What is a lithospheric plate and how do they move?
The plates make up Earth's outer shell, called the lithosphere. (This includes the crust and uppermost part of the mantle.) Churning currents in the molten rocks below propel them along like a jumble of conveyor belts in disrepair.
What force causes seafloor spreading?
The motivating force for seafloor spreading ridges is tectonic plate slab pull at subduction zones, rather than magma pressure, although there is typically significant magma activity at spreading ridges.
What can you say about the thickness of the sediments far from the ridge thicker or thinner?
As you move away from the ridge spreading center the sediments get progressively thicker (see section 4.5), increasing by approximately 100-200 m of sediment for every 1000 km distance from the ridge axis.
Where is seafloor sediment thickest?
Sediments are typically laid down in layers, or strata, usually in a body of water. On the seafloor, sediments are thinnest near spreading centers (young seafloor) and thicker away from the ridge, where the seafloor is older and has more time to accumulate. Sediments are also much thickest near continents.
How does ridge push cause plate movement?
Ridge push –magma rises as the plates move apart. The magma cools to form new plate material. As it cools It becomes denser and slides down away from the ridge. This causes other plates to move away from each other.
How does ridge push affect plate movement?
Ridge Push. Gravitational force that causes a plate to move away from the crest of an ocean ridge, and into a subduction zone. It works together with Slab Pull, but is much less significant.
What process explain the thickening of the lithosphere?
Thickening of lithospheric plates is best explained by understanding that: collision of continental plates pushes rocks of the same density together. The temperature of ocean rocks is coolest near midocean ridges and increases as rocks get closer to continental margins.
What happens to oceanic lithosphere as you move away from a mid-ocean ridge quizlet?
As lithospheric plates move away from midocean ridges, they cool and become denser. They eventually become more dense than the underlying hot mantle. After subducted, cool, dense lithosphere sinks into the mantle under its own weight. This helps to pull the rest of the plate down with it.
Why does the lithosphere 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.
What layer causes the lithosphere to move?
1 Answer. The theory of plate tectonics suggests that the lithospheric plates move because of convection currents in the semi molten mantle.
Why does lithosphere 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.
What happens when Seafloor spreading occurs?
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 causes seafloor spreading 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.
Where are the thickest sediment deposits and what type of sediments are they likely to be?
Sediments are typically laid down in layers, or strata, usually in a body of water. On the seafloor, sediments are thinnest near spreading centers (young seafloor) and thicker away from the ridge, where the seafloor is older and has more time to accumulate. Sediments are also much thickest near continents.
How thick is the seafloor?
Ocean Floor Volcanism and Construction of the Crust On average, oceanic crust is 6–7 km thick and basaltic in composition as compared to the continental crust which averages 35–40 km thick and has a roughly andesitic composition.
Why are bottom sediments thickest near continents?
This is because the crust near passive continental margins is often very old, allowing for a long period of accumulation, and because there is a large amount of terrigenous sediment input coming from the continents.