Tectonic Plates

Earthquakes and volcanoes make major changes to Earth’s crust and they happen mostly where tectonic plates meet. Other changes in the Earth’s crust such as canyons forming or rivers widening is caused by weathering and erosion.

Lava is made of molten rock and it rises from inside the earth. This observation suggests that the inside of the earth is hot and is also made of rock (at least near the surface).

Earthquakes occur when large pieces of the Earth’s surface called tectonic plates move. Sometimes the plates move abruptly releasing built up pressure which causes the ground to shake and crack. Most earthquakes happen where tectonic plates meet.

Mountains can be formed as a result of two tectonic plates coming together. A valley might form from plates moving away from each other.

The eastern coast of South America and western coast of Africa look like they might fit together. This was the simple observation that started the search for evidence to support the idea that continents could move and that they were connected in the past.

If we can understand how the plates move, we could potentially predict earthquakes and volcanic eruptions. Currently we know where the plate boundaries are, but have not found ways of predicting exactly when these disasters will happen.

The Earth’s crust is the top layer. Next comes the mantle which is made of hot solid rock that can move very slowly over years. The inner-most layer is the core. The core is the hottest but is a solid due to being made mostly of iron and nickel under intense pressure from all the rock above it.

Convergent boundaries are where boundaries move towards each other. Divergent boundaries are when plates move apart. Transform boundaries are when plates slide past each other.

Pangea is a super continent predicted by the theory of continental drift. Scientists believe that about 240 million years ago all the continents were one large one called Pangea. The land of Pangea then broke apart due to tectonic plate movement and moved over millions of years. This idea is well supported by multiple lines of evidence.

Subduction occurs when two plates converge, and one slides under the other. This is common when continental plates meet oceanic plates. Because the oceanic plate is denser, it slides under the continental plate.

Uplift occurs when two plates converge and force land upwards creating mountains. The best example of this is the Himalayan Mountains. These huge mountains were formed by the Indian plate and Eurasian plate converging over more than 50 million years.

Convection is the process of warm fluids rising and cooler fluids sinking. Inside the Earth, convection is powered by heat mostly from the core. The slow circulation of rock in the mantle moves the tectonic plates at the surface.