Transcript: There are three basic types of rocks found on the Earth. The first are called igneous rocks. These form from molten material that is cooled and solidified. They are very common in the rocks of the Earth's surface. Granite and basalt are two examples. Earth is a restless place, and the second major type is called sedimentary rocks. You might think that wind, sun, and rain can have little effect on something as hard as a rock, but acting over millions of years, erosion can take an enormous toll on a surface of a rock. Wind and rain cause erosion, and erosion acting over millions of years breaks down rocks and turns it into small particulate matter that is washed by rain and rivers down to the ocean and into stream beds. These layers, as they're deposited and compressed, create sedimentary rocks. Two examples are sandstone and limestone. The third major type of rocks are metamorphic rocks. Earth is a restless place in its interior as well, and very few of Earth's rocks have remained unchanged for the history of the Earth. Metamorphic processes occur when igneous or sedimentary rocks are modified by extreme heat or pressure or sometimes hot water in the presence of acidic solvents. These materials fundamentally change the structure of the rock. Marble is an example.