The Earth’s mantle is composed of hot, convecting rock. The heat for this convection comes from the Earth’s hot core. The mantle circulates in slow currents, with the hotter material rising and the cooler material sinking.
This movement of the mantle drives plate tectonics. The lithosphere (the solid outer layer that includes the crust) sits on top of the mantle. The lithosphere is broken into a number of large and small plates that move around on the surface of the planet.
Convection currents in the mantle cause these plates to move. Where a convection current is sinking, it pulls on the lithosphere above it, moving the plate along with it.
PLATE TECTONICS
If you’re like most people, you probably think that plates move around on Earth’s surface because of convection currents. But how do these currents actually work? And why do they cause the plates to move?
Convection currents are created when hot material rises and cooler material sinks. This can happen in fluids (liquids and gases) or in solids, like the mantle of the Earth. When hot mantle material rises, it pushes on the lithosphere (the solid outer layer that makes up the Earth’s crust), causing the plate to move.
Why does hot mantle material rise in the first place? It’s all due to heat transfer. The hotter something is, the more energy it has.
So when hot mantle material comes into contact with cooler lithosphere, some of that heat is transferred from the mantle to the lithosphere. This makes the lithosphere warmer, which causes it to expand slightly. As it expands, it becomes less dense than the surrounding mantle material and starts to rise.
This process repeats itself over and over again, causing convection currents within the mantle and resulting in plate tectonics.
Why Do Plates Move Convection Currents
Plates move convection currents because the Earth’s mantle is a fluid. The mantle is heated by the core, and this heat makes the mantle less dense. The less dense mantle rises, and cooler, more dense mantle falls.
This movement of the mantle creates convection currents.
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How Do Convection Currents Move the Plates?
The Earth’s outermost layer is made up of several large pieces, called tectonic plates. These plates are constantly moving around on the planet’s surface. Sometimes, they move apart from each other (divergent boundaries), and sometimes they move towards each other (convergent boundaries).
At convergent boundaries, one plate usually slides underneath the other (subduction).
Convection currents play a big role in moving the Earth’s tectonic plates around. Convection occurs when hot material rises to the surface, while cooler material sinks down.
This movement creates a circulating current. The hot mantle material beneath the Earth’s crust is less dense than the colder crust material above it. So, it rises up towards the surface.
As it rises, it pushes the crustal plates aside. The mantle material then cools off and sinks back down again. This cyclic motion of convection currents slowly moves the Earth’s tectonic plates around over time.
What Happens When a Tectonic Plate Sinks?
When a tectonic plate sinks, the process is called subduction. This happens when one plate slides underneath another and both plates are moved towards the Earth’s mantle. The mantle is made up of hot rock that slowly moves and this helps to push the plates around on the surface.
The sunken plate becomes heated and starts to melt which forms magma. Magma is less dense than solid rock so it rises up through cracks in the overlying plate.
How Do Plates Move When the Ground is Shaking?
When an earthquake occurs, the shaking of the ground causes stress on the Earth’s crust. This stress is transferred to the plates, causing them to move. The amount of movement depends on the size of the earthquake and the type of plate boundaries involved.
At transform boundaries, plates slide past each other horizontally. The amount of horizontal slip during an earthquake is usually much less than the vertical slip that occurs at other types of plate boundaries. However, because transform boundaries are usually found in highly populated areas (such as along California’s San Andreas Fault), even small amounts of horizontal slip can cause damage.
At convergent boundaries, one plate moves under another and both plates sink into the mantle. The sinking motion is accompanied by an increase in heat and pressure, which melts some of the rock on both plates. This molten rock (magma) rises to the surface and can erupt from volcanoes.
Earthquakes at convergent boundaries are often large and can cause extensive damage due to both the shaking of the ground and eruptions of magma.
At divergent boundaries, two plates move away from each other as new crust forms between them. The most well-known example of this is mid-ocean ridge spreading, where hot mantle rock rises up and pushes against cold oceanic crust.
As this happens, earthquakes occur along faults that form between the two plates.
How Do Plates Move Where Convection Currents are Rising Quizlet?
Convection currents are caused by differences in temperature. Warm air rises and cooler air sinks, creating a current. The warm air rising pushes the cooler air out of the way, causing it to circulate.
This circulation is what we feel as a breeze.
Conclusion
The Earth’s mantle is made up of hot rock that is always moving. The upper part of the mantle is called the lithosphere. The lithosphere is broken into large pieces called plates.
Plates move on the asthenosphere, which is the layer below the lithosphere. The asthenosphere is also made up of hot rock, but it’s softer than the lithosphere so the plates can move around on it.
Convection currents happen when hot rock rises to the surface and cooler rock sinks back down.
The convection currents in the mantle are what cause plates to move.
