The Rock Cycle in Canada

What do a computer, a stove and a sidewalk have in common? OK, maybe you use them all every day, but there’s more. All three of these items contain rocks! In fact, if you look carefully, you’ll find that many other objects you use every day also have rocks in them.

Of course, some rocks are more obvious than others. Depending on where you live, you might be surrounded by rocks. But do you know what kind of rocks they are?

What Are the Different Types of Rocks?

There are three types of rocks:

• Igneous rocks

• Metamorphic rocks

• Sedimentary rocks

Igneous Rocks

Igneous rocks come from magma, a hot material in the Earth’s crust. When magma reaches the Earth’s surface, usually out of a volcano, it’s called lava. When it cools, it becomes igneous rocks. 

Igneous rocks that form beneath the Earth’s surface are called intrusive igneous rocks. Igneous rocks that form above the Earth’s surface are called extrusive igneous rocks.

Balancing Rock in Nova Scotia is made of an igneous rock called basalt.

Sedimentary Rocks

Sedimentary rocks are formed from loose sediment over millions of years. Sediment is any solid material that gets moved from one place to another. Rocks and minerals can be sediment. Plant and animal remains can be sediment, too. Sediment can be as small as a grain of sand or as large as a boulder. Over time, sediment builds up and becomes sedimentary rock.

The Earth’s surface is composed of 75% sedimentary rock. Let’s look at some examples here in Canada. 

Cape Spear, Newfoundland and Labrador, is the most easterly point in North America. Its cliffs are made up of sedimentary rock.

Percé Rock is a natural arch off the coast of the Gaspé Peninsula in Quebec. It is made of limestone, another type of sedimentary rock.

Badlands, which are found in several parts of Canada, are examples of sedimentary rock formations. They tend to form in areas where rain tends to fall in short bursts, like in a thunderstorm. You may have seen badlands in Alberta’s Dinosaur Provincial Park or in Cheltenham, Ontario.

Metamorphic Rocks

Metamorphic rocks are igneous or sedimentary rocks that have been transformed by pressure or heat. The heat and pressure can come from inside the Earth, from the shifting of the Earth’s crust or from radioactive decay. These forces change the rock’s structure.

Did you know?

Some of the world’s oldest known fossils were found in the Canadian Shield. Fossil bacteria and algae in the region have been dated to about 2.2 billion years ago.

What Is the Rock Cycle?

The rock cycle is the process by which one type of rock becomes another. 

Most rocks begin as igneous rocks. Over time, wind and water break them up into sediment. This is called erosion. As sediment piles up, it becomes sedimentary rocks. Eventually, these rocks are covered up and become part of the Earth’s crust. There, heat and pressure build up and turn these rocks into—you guessed it!—metamorphic rocks.

The different types of rocks can change into each other over millions of years. This cycle is especially cool because it can go in any order. One type of rock can change into either of the others!

You can see evidence of the rock cycle all around you! For example, when pieces of cliffs or large rocks are eroded (worn down), they create sediment. Water is often responsible for eroding rocks. The next time you’re walking by a stream or river, look for smaller pieces of rock that have been eroded. After millions of years, they may become a different kind of rock!