Earth's surface has changed greatly since the beginning of time and is still changing today. With the use of modern technology, scientists can observe how the Earth's surface changes over time.  Sometimes scientists cut down into the Earth's surface, looking at it in a cross section, or they take a picture from above called an aerial view. Changes can originate from below the surface and are caused by earthquakes and volcanoes.  The surface of the Earth can also be changed by an impact from outer space, such as from a meteor strike.  Most commonly, however, the changes to Earth's surface are due to weathering and erosion.