Geology of British Columbia

British Columbia is physically impressive: prehistoric mountain ranges, highlighted by the impressive Rocky Mountain range, stack up against each other.

British Columbia's mountain ranges are separated by plateaus in the lower elevations. Sections of BC reach far into the northern hemisphere, meaning relatively recent ice ages have been pivotal in its terraforming. Bordered by the Pacific Ocean along its west coast, BC is naturally part of the geologically active region known as the Pacific Rim. Plate movements are especially mobile along the southwestern edge of BC, near Vancouver Island. British Columbia's land history is laid bare for enthusiasts to discover and witness the creation of more!


Ranges & Valleys

British Columbia can mostly be divided into five vertical line sections. These coincide with a series of mountain ranges separated by low lands of varying condition. Differing styles of rock compose each unique range. Northern reaches of BC have been geographically measured as older than southern regions.

The westernmost mountain range in BC is known as the Insular Range. The Insular Range formation is comprised of rocks that make up the islands along the coast, including Vancouver Island and the Queen Charlottes. Ice ages in the past have dried enough of the ocean that the seafloor between the islands and mainland was exposed. The Insular Range features a mix of sedimentary and volcanic rock. One of the highest peaks in this range is the Golden Hinde, reaching over 6600 feet. For comparison sake, mountains in the interior ranges reach as high as Fairweather Mountain at 15,000 feet!

British Columbia's mainland Pacific coastline is made up of the Coast Mountains. The Coast Mountains extend from the Alaskan border in the northwestern section of BC along the ocean all the way south to the border with Washington State. Very few sand beaches exist in this rocky, volcanic environment. A few rivers carve their way through the range, most notably the Fraser River in the Southwest. This mountain range, formed by prehistoric eruptions, is almost 200 miles wide and 1000 miles long. Granite and other metamorphosed rock comprise their make up. Glacial ice still covers great sections of the Coast Mountains where BC's border moves away from the ocean along its border with Alaska, where sits Fairweather Mountain.

The Interior Plateau sits in between the mountain ranges of British Columbia. It especially is situated center province and south of the Interior Mountains. This is the least rocky geologic portion of BC, containing most of the 3% of provincial land that is farmable. Four named sections of this plateau exist: the Cariboo, Chilcotin, Nechako, and Thompson plateaus. Boundaries for these include rivers and mountains.

East of the Interior Plateau region, the Columbia Mountains streak north from the United States border until forming into the Interior Mountains. Geologic makeup of this zone means several smaller ranges have collided to create the greater whole. Since this amalgamation of rocky structures is less uniform, there are a number of passes between interior communities. Some of the world's favored geologic explorations occur in this region.

Finally: the Rocky Mountains. North America's great range runs along the eastern border of British Columbia. The Rocky Mountains lies in northeastern BC where the range finds one of its ultimate ends--the other end being over 3000 miles away in the United States' New Mexico. Sedimentary rocks dating back over 2 billion years comprise much of the range. The Rocky Mountains Trench is situated along the western edge of the mountains. Headwaters of the Columbia, Fraser, Kootenay, and other major rivers can be found in this 900-mile stretch.


Ice Age Effect

British Columbia's coastline is a testament to the power of ice. Deep fjords formed from sheering ice evidence trace BC's geologic history. 35,000 years ago, the Fraser Glaciation began in earnest. Advancing fields of ice covered interior regions as well, stopping near the southern edge of BC. lateaus in the center of British Columbia are also riddled with signs of the last Ice Age. Further, a pair of large icefields can be found along the eastern and western edges of BC. The Columbia Icefield, along the Alberta border in the Rocky Mountains, is the largest in the range. The Juneau Icefield helps to define British Columbia's border with Alaska. It is one of the largest ice fields in the West. Both have seen a major trend toward retreating ice in recent years. Tourist opportunities are offered to help individuals experience the power that is ice in action!

Glacial Terminology 

Erosion is the primary chiseling tool of glaciers. When the massive amounts of ice move across bedrock, but do not carve it out, this is called abrasion. Quarrying is when the glacier actually removes pieces of the underlying bedrock. Everything that is moved by a glacier has to be put somewhere else. This is called deposition. It mostly takes place while ice is retreating.

Moraines, uneven ground across the relative flatness of the low lands between valleys, are created by deposition. These include ridges, washboard mounds, and oddly shaped soil and rock structures. Material of all sorts them be found in these moraines. Clay, sand, rocks, and other molecular combinations get all mixed up through the process of glacial movement.


Plate Tectonics

British Columbia's land, especially along the western edge, is affected and formed by massive plates that are still moving today. Three types of boundaries construct the way these plates interact with each other. These interactions are called tectonics. When movements occur violently enough, plate tectonics create earthquakes. BC is rich in earthquakes.

Convergent tectonics are the most apparent and possibly destructive to people in British Columbia. The Juan de Fuca Plate is pushing underneath, the act of subduction, the North American Plate. This region is known as the Cascadia Subduction Zone. It runs from Northern California to Vancouver Island. Pushing Earth's crust beneath other parts of Earth's crust can lead to the creation of mountains.

Volcanoes and earthquakes are both fueled by the natural act taking place in Earth's crust. British Columbia's most recent eruption took place at Mount Meager in approximately 300 BC. Contrary to the millennia separating us from volcanic activity in British Columbia, earthquakes strike the region frequently. A 4.7 on the Richter scale, powerful enough to wake people though only minor damage and no injuries were reported, shook Victoria in December 2015.

The most powerful earthquake in Canadian history took place at the strike-slip Queen Charlotte Fault in 1949. It was an 8.1 on the Richter scale. Strike-slip faults are sometimes referred to as transform faults. These occur when two plates strike against each other while moving in opposing directions. In this scenario it was the North American Plate and the Pacific Plate.

Least destructive among the plate tectonics in British Columbia are those classified as divergent. There is a place under the ocean, not quite 175 miles off the coast of Vancouver Island, where the Juan de Fuca Plate is pulling away from the Pacific Plate. This is creating an opening for magma to seep onto the sea floor and create new ocean crust. British Columbia, a place that already offers so much to so many, is working on growing more land, just for you!