Position

• Although it might appear that the Earth's crust is made of one uniform piece, it is actually constructed out of a series of plates that move against each other. The majority of the crust is made out of nine plates, with smaller plates shifting in between the larger ones. Each continent is attached to a plate, and large plates also lie underneath the ocean floor. These plates are in a constant microscopic state of movement.
  
  

Material Composition

• The vast pressures that appear in the Earth's crust, combined with heat and other elements, take materials and transform them into different ones. This is the process by which fossil fuels are created. As carbon-based material, such as forests and swamps, slowly becomes compressed into the crust of the Earth, millions of years of pressure eventually transforms that material into fossil fuels. Compression and time can also affect minerals in different ways. Diamonds, for instance, are also formed under high pressure deep within the crust.
  
  

Sudden Shifts

• Usually, the plates that make up the crust of the Earth move very slowly. However, the plates sometimes press together tightly and are unable to move. When this happens, the force beneath the plates that fuels the movement continues to push on them. The result is a slow build of pressure that mounts until the plates finally slip and shift. The sudden slip and shift is what causes earthquakes. The shaking felt on the surface is the dissipation of the vast amount of energy pent up by the stuck plates.
  
  

Magma

• The crust is also changed by the passing of molten magma through it. The molten rock is forced out of the mantle up through the crust of the Earth. Intense pressure and heat causes a reaction that forms the molten rock. This magma is not as dense as the rock around it, so it comes to the surface. Once it penetrates the crust, it becomes lava. Thinner magma slowly oozes out and builds up land formations on the crust as the rock hardens, such as the many volcanic islands in the Pacific ocean. If the lava is thick and can't flow easily, pressure builds and eventually results in a destructive volcanic explosion.