Difference Between Convection Current Vs. Plate Tectonics
The Earth’s surface is formed and changed by geologic forces that are set in motion by the heat from inside the Earth. The Earth’s core has a temperature of about 12,600°F (7000°C). The escape of this interior heat and the heat from radioactive decay provide the energy that forms mountains and volcanoes and causes earthquakes.
To understand how heat provides the energy for geologic forces, imagine the movement of boiling water in a pan. As water at the bottom of the pan becomes hot, it becomes lighter and rises to the surface. When the heated water reaches the surface, it moves to the side of the pan. Here it cools and becomes heavier. This causes it to sink to the bottom. This movement caused by heating and cooling is called a convection current.
A similar process is believed to exist inside the Earth. Convection currents bring hot material called magma up through the Earth’s mantle toward the crust. As the magma cools, it circulates back into the Earth’s interior. In places the magma breaks through the crust, creating volcanic eruptions. Geologists studying the ocean floor have discovered volcanic mountain chains where convection currents reach the Earth’s crust. These underwater mountain chains are found in the middle of the Atlantic, Pacific, and Indian oceans.
As magma erupts along the mountains on the ocean floor, it creates new crust and pushes existing rock sideways. This force, along with the horizontal movement of convection currents, is immense. In fact it slowly moves huge blocks, or plates, of the Earth’s surface. The geologic activity caused by the movements of these plates is called plate tectonics.
These plates move only a few inches a year. But during the last few hundred million years they have moved thousands of miles around the Earth. A map of the Earth 225 million years ago would look very different from a map of today. Africa and Europe were joined to North and South America. The Atlantic Ocean did not yet exist. Australia and Antarctica formed one large continent. And India was a large island. Earlier still, there was only one supercontinent named Pangaea (as had been proposed by Alfred Wegener in 1912). The rest of the Earth was covered with water.
Today the Earth consists of seven large plates and several smaller ones. Most plates include parts of both continents and oceans. Geologists have also discovered that parts of Alaska, western North America, and other places are made up of dozens of small pieces of plates. These fragments have collided with and stuck to larger plates. Almost all earthquakes, volcanic activity, and mountain building take place where the edges of plates meet.