Types of Rocks In Banff National Park: A Guide To the 3 Most Common You'll Spot

Banff National Park, located in the Canadian Rockies, is Canada’s oldest national park, and home to many pristine rivers, waterfalls, mountains and glaciers that attract millions of visitors every year.

The Park boasts many awe-inspiring hiking trails, but if you want to take in the beauty of all that Banff National Park has to offer, there’s no better way than by learning about its rich geology.

Types of Rocks In Banff National Park: A Guide

The Rockies consist of sedimentary rocks.

Sedimentary rocks are formed as layers of mud, sand, gravel and organic matter that accumulate on the Earth’s surface.

The mountains were created over millions of years by compressional forces moving Earth’s crust around to form trenches, folds and faults to create the current landscape we see today.

The Rocky Mountains themselves were formed when the North American and Pacific Plates collided.

The compression of these two plates caused material like silt, mud and sand to be scraped up off the land and pushed into the Rocky Mountain Trench in Canada.

The collision between these two plates also formed faults in the Earth where rocks on either side move past each other or one slips underneath the other, forming a strike-slip fault like the Lewis Overthrust Fault in Montana.

The mountains themselves are made up of sedimentary rocks because they were formed from eroded material or scraped off the land to form layers.

There are three main types of sedimentary rocks: clastic sedimentary rock, organic sedimentary rock and chemical sedimentary rock.

Clastic sedimentary rocks are formed from particles that have been broken down into sand, silt or clay fragments. These fragments are then laid down over time to form layers.

Organic sedimentary rocks are usually formed at the bottom of oceans or lakes.

They are created when dead plants and animals in these aquatic environments decay and then condense into layers.

Chemical sedimentary rocks are formed by precipitation of minerals from geologically-sourced water, such as precipitation of calcium carbonate.

If you are on the hunt for rocks during your visit, here are the three most common rocks you’ll spot in Banff National Park:

Sandstone

This sedimentary rock is most likely to be found in the Park.

The formation of sandstone occurs through a process called cementation, where grains of sand and other particles stick together with dissolved material like quartz and calcite.

There is an abundance of sandstone here because it is formed from sand.

Even though sandstone can form anywhere, there was a large amount of sand available to be deposited as sediment during the formation of the Rocky Mountains.

Sandstone is a clastic sedimentary rock, which means it forms from fragments of other rocks being cemented together over time.

The type of rock that sandstone comes from determines its color and texture. For example, sandstone can be formed from granite or shale.

Sandstones formed from granite are usually light tan or rose-colored.

On the other hand, sandstones formed from shale are darker in color because of the presence of iron sulfide minerals called pyrite.

Shale

Shale is another rock that you will find in abundance in the park.

Shale is a sedimentary rock whose properties make it highly desirable for the production of natural gas and oil.

Along with other unconventional sources of energy such as tar sands or oil shale, shale has become a key player in today’s global oil market.

Shales are dark, fine-grained sedimentary rocks rich in organic material.

These rocks are not easily permeable to liquid or gas, which is why they are rarely found as liquid or gas reservoirs.

Shale gas and oil are usually trapped inside shale rock formations by natural impermeable seals of other rocks.

Because these wells cannot produce enough liquid or gas to be commercially viable at current prices, producers drill wells and use horizontal drilling and hydraulic fracturing to release the gas or oil from shale formations.

These wells are very expensive, which is why producers have chosen to drill in various spots where the costs of drilling are offset by high yields.

Rocks containing shale are not uncommon in Banff National Park.

They typically form at higher elevations beneath glacial ice or in alpine regions.

The shales can be weathered and broken down into soil, which is then carried down to lower elevations by water or glaciers.

The rock can also be eroded and redeposited at the same elevation it originated at.

This allows for shale to form widespread at higher elevations in many areas in the Park.

Limestone

Limestone is a sedimentary rock composed mainly of calcium carbonate.

Its formation occurs in areas of the park where calcium carbonate-rich water has been spilt by the sea.

The spillage forms a chemical deposit that solidifies into limestone, which is then compacted further because of its own weight.

Limestone in Banff National Park resembles other typical limestone features such as caves, sculpted rock surfaces, and sinkholes.

There is a variety of plant life associated with limestone areas.

Limestone bedrock is the foundation for many mountain streams in Banff National Park.

The water that flows over limestone bedrock picks up carbon dioxide, which is the end product of photosynthesis involving microscopic plant life called lichens.

The carbon dioxide acts as a weak acid when released into water, lowering its pH and making it quite corrosive.

In this way, carbon dioxide from limestone can alter the landscape through erosion and dissolution in surface streams.

One example is Johnston Canyon, where the acidic water has created a striking gorge.

Limestone bedrock can be seen from the valley bottom at the Cave and Basin National Historic Site.

This is where the park was established in 1885 to protect Banff Springs, which were discovered by John Glenn in 1882.

In the early days, visitors were drawn to the springs for their supposed healing properties. The site also features a reconstruction of the original hot spring bathing pool.

Banff limestone is a relatively new geological feature.

It is estimated to be between 70 and 90 million years old.

This means that during the last ice age, Banff was repeatedly submerged under a vast body of water called a seaway from about 70 to 40 million years ago.

For this reason, fossils are rare in the mountains of Banff National Park.

Whether you are visiting Banff National Park to see the Lower and Upper Falls, Johnston Canyon or the Cave and Basin National Historic Site, knowing the landscape and geology of this amazing park is another way to enrich your experience.