Landform

Volcanism produces a number of landforms. First, of course, are volcanoes themselves. These may be steep sided cinder cones, gently sloping shield volcanoes constructed of lava flows, or a combination of the two, called composite volcanoes, or strato-volcanoes. Cinders and ash fall out of the air and accumulate in steep-sided piles, but these are easily washed away by agents of erosion so they are rarely very large. Solidified lava flows are much more resistant to erosion, but because the lava flows downhill easily before it cools, their slopes are usually very gentle. The composite volcanoes have layers of ash, giving them substantial slopes, protected from erosion by layers of lava. Many of the most famous volcanoes, such as Mt. Fuji, are composite.

Like any fluid, molten lava flows downhill, moving down valleys and off ridges. Frequently it will cool and solidify in the valleys, forming a rock which is very resistant to weathering and erosion. As time goes by, the surrounding softer rocks may be eroded away, leaving the lava flows at a higher elevation, protecting the rock beneath them from erosion. In this way "inverted topography" is developed, where those areas which were lowest become the most elevated.