The Processes that Shape Landforms

When it comes to landforms, Canada pretty much has it all. There are mountains and valleys, rolling hills and plains, and even some fjords!

A landform is any surface feature on Earth. Landforms create the planet’s different natural landscapes. They provide homes for wildlife and humans. A place’s landforms make up its topography. In other words, topography is how landforms are laid out in a particular area.

Landforms can create stunning views. The topography of a place like the Grand Canyon can be downright spectacular. But what's really interesting is how these landforms develop and disappear!

Did you know?

Topography is the study of land surfaces. This includes geography and differences in elevation. These changes in height are called relief.

Weathering is one major process that shapes different landforms. Temperature and precipitation both contribute to weathering. So does pressure on rocks, minerals and soil. These are examples of mechanical weathering. Chemical reactions can also cause rocks, minerals and soil to break down. 

What is mechanical weathering?

Mechanical weathering breaks the Earth’s materials apart. 

One example is frost weathering, which is sometimes called cryofracturing. It happens when water gets into tiny cracks in rocks. The water expands when it freezes, causing the rock to break apart. As the freeze-thaw cycle continues, more water can get into the cracks and break the rock apart even more.

Pressure from inside the Earth can also cause mechanical weathering. Liquid rock called magma is trapped under the planet’s surface, along with different gases. These materials are very hot and under a lot of pressure. When magma and gases rise toward the surface, they sometimes create cracks that release the pressure. That’s what happens when a volcano erupts! 

Did you know?

Magma is molten rock found under the Earth’s surface. When magma reaches the surface, it’s called lava.

What is chemical weathering?

Chemical weathering changes in the chemical properties of materials on Earth’s surface. 

One example is carbonation. It happens when acid rain falls on rocks that contain calcium carbonate (CaCO3). For instance, limestone often breaks down because of carbonation. The sulfuric acid in acid precipitation reacts with the limestone. This replaces the rock with a new chemical product, called calcium bicarbonate Ca(HCO₃)₂.

Oxidation also causes chemical weathering. Oxygen in the air reacts with chemicals in different landforms. Colour change is a common sign of oxidation, especially in rock formations that contain a lot of iron. When iron is exposed to oxygen, a redox reaction produces iron oxide. That’s a fancy word for rust! 

Did you know?

Copper also changes colour as it oxidizes. The copper roof towers of the Parliament Buildings in Ottawa are known for being green. Thanks to some new copper, they now look more like pennies!  

What other geological processes affect landforms?

Erosion is another geological process that creates landforms. 

When mechanical and chemical weathering breaks up materials on the Earth’s surface, erosion can move them to new locations. For example, wind, water or ice can create a valley by removing material. Plateaus can also be formed this way. 

Of course, the material that gets carried away doesn’t just disappear. When layers of eroded material pile up, it’s called deposition. This can create new landforms. For example, coastal deposition is how beaches are formed. When eroded material is deposited at the mouth of the river, a river delta is formed.

The constant downward pull of gravity can also change the landscape by creating new landforms. Gravitational erosion can involve small bits of soil slowly tumbling down a hill over many years. Or it can involve giant slabs of soil or rock suddenly giving way in a landslide. 

There are many other forces that shape landforms on Earth. People have built entire careers on studying how these features form and change. Geologists, geographers and other Earth scientists are constantly finding out more about our planet's fascinating topography!