An Overview: The Shaping of Western Canada

The earth’s history is one of constant, but very slow change. People measure time in hours, days, months, and years, but Earth time is measured in millions and billions of years. The oldest rocks that have been found are about 4 billion years old! To better understand and classify the events that make up the world’s history this vast expanse of time has been divided into eons, eras, periods, and epochs. Each of these divisions have been set by significant evolutionary events in earth history. For example: the boundary between the Proterozoic and Phanerozoic Eons was established by eighteenth century geologists in Europe because there was an obvious difference between the overlying Cambrian (Phanerozoic) rock and the Precambrian (Proterozoic) rock that lay beneath it. The Cambrian rock was stratified (layered), fossil-bearing sedimentary rock while the Precambrian was crystalline igneous (volcanic) and metamorphic (changed by heat, pressure, and stress) rock.

The term Phanerozoic takes its definition from two root words, phaneros which means "evident" and zoon which means "life". In the term Proterozoic the key root is protoera which means "minute or microscopic". Therefore, this boundary displays a significant change in the fossil record and the evolution of our planet. Further study has revealed that this change occurred 570 million years ago!

The world we know today is the result of volcanism, plate tectonics, and erosion.

The crust upon which the continents are built is made up of volcanic, or igneous, rock. The granite (an igneous rock) of the Canadian Shield is an example of this. However, the Canadian Shield was not created by one huge volcanic event, but by the accumulation of several pieces, called terranes or provinces, that were pushed together through the processes of plate tectonics. This pushing together of terranes is called accretion.

The Canadian shield is only a portion of what would eventually become the continent of North America. In western Canada the accretion of more terranes has resulted in the land masses that we know as British Columbia. As well, this process is not finished; Vancouver Island will eventually become part of the mainland.

The enormous force that is required to move these land masses not only pushes them together, but continues after contact is made. These great pieces of continental crust are pushed together very slowly and with such force that the rocks begin to bend and compress. Sooner or later something has to give. This results in the faulting or breaking of the rock.

The North American Cordillera began as an island arc of volcanic origin. At the same time the western edge of the Canadian Shield was the western coast of what we now know as North America. Over time the cordillera grew the area between it and the Canadian Shield became lowlands and this area is now known as the Western Sedimentary Basin. This basin extends from the Gulf of Mexico to the Arctic Ocean. At various times throughout prehistory this area has been both above and below sea level and, consequently, experienced periods of erosion, and sedimentary deposition.

Most people view erosion on a relatively small scale: streams and rivers moving sediment, chunks of earth being washed away during a rain storm, and wind erosion. These forces combined with the immense erosionary and transportational abilities of glaciation and coupled with the force of gravity, wear down all exposed land and deposit the materials (deposition) in low lying areas including lake and ocean floors. Geologists see the big picture, they view the effects of erosion over thousands and millions of years; they often refer to erosion as mass wasting. Depositional environments have created the rock structures upon which Lloydminster sits. The preserved sediments in the Western Sedimentary Basin exceed 6 km in depth, it has been estimated that an additional 2 to 9 km of sediments have been removed since Eocene time (began 58 mil. years ago).The most important depositional environments, to present day Lloydminster, occurred when this area was covered by sea water. Sea environments teem with life, and it is the metamorphosed remains of these organisms that we pump out of the ground in the form of oil.

To properly understand how geologic force have shaped our world we must first understand that these processes do not create new mass, mass is merely redistributed; the earth is the ultimate recycler. When mass is added to one part of the earth it has been taken away from another. Another very important consideration is continental drift. This drift is the result of plate tectonics, and through it the position and climate of the various regions of the earth have changed drastically and repeatedly throughout the eons of time. Through these processes not only has the environment of Antarctica been tropical at times, but at various times our area has been close to the equator with a tropical climate.

Through a large portion of earth time, our area has been in a coastal, a shallow, or an epeiric (a warm shallow inland sea) marine environment. This has allowed for the deposition of the thousands of feet of sedimentary rock upon which our town is built. Other areas of the world that are now coastal were at times part of an inner continent and experienced the associated arid climate.

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