Landforms are defined as specific features that appear on the Earth's surface. Some examples are mountains, plains, plateaus, valleys and hills. What causes these landforms are different forces that work internally and externally on the Earth's surface and core to form some of Earth's natural features.
Layers of the Earth
Earth is made up of four layers: the inner core, the outer core, the mantle and the crust. Moving from the inner core to the crust, temperatures go from extreme heat to about room temperature. The inner core is a hot ball of mostly iron under extremely high pressure. The outer core is made up of mostly melted iron. The mantle is a thick liquid made up of iron, magnesium, aluminum, silicon and oxygen. The crust is made up of a mixture of solid minerals and is breakable.
The Earth's crust is broken into plates that lie over the mantle. Because the mantle is hotter toward the interior and cooler toward the exterior, convection currents occur, which causes the plates to move above them. The edges of the plates are called plate boundaries. Volcanoes, earthquakes and mountain building or orogeny are found along plate boundaries.
There are three different plate boundaries: divergent, convergent and transform. Divergent boundaries are where plates pull apart and lava pushes up into the space created. This forms most of the Earth's new crust. Plates are pushed together along the convergent boundaries and plates slide past one another along transform boundaries.
Faults are a kind of transform boundary. Faults are a fracture or break in the Earth's crust along a line of weakness. Faulting can be caused by tensional or compressional forces put on rocks either laterally or vertically. An example of a fault is the San Andreas Fault in California. A block mountain, or horst, is another example of a fault. A block mountain has a flat surface and overhanging cliff and is formed when faulting in the crust causes a block of the crust to be lifted.
External or Internal Processes
Landforms can also be shaped by external or internal processes, which work on the crust of the Earth. External processes work on the surface of the crust through weathering, denudation (or removal of the surface), erosion and deposition (or the raising of land). Some of these works are caused by rivers, glaciers, winds and waves. Internal processes work on the interior layers of the Earth. Forces gradually build up and the crust will undergo movements in the Earth such as earthquakes, volcanic activity or mountain buildings.
Folding is a type of internal process on the Earth. Folding happens when forces on the Earth's crust push toward each other from opposite directions, which bends and folds the rock layers in different ways.
About the Author
Veronica Ouellette began writing professionally in 2007 as an editorial assistant for the "Stamford Advocate." As a freelancer, her work has appeared in numerous online publications. She earned a Bachelor of Arts in English from the University of Massachusetts at Dartmouth.