BC Biodiversity Pages

Quartz Veins

Above: A small quartz vein embedded in igneous rock, Right: a much larger piece of the quartz vein embedded in igneous rock but this one is still beneath the surface of the water in Chapman Creek, the creekbed there cuts through a large portion of this. Quartz veins often are found in igneous rocks because quartz is made of Silicon and Oxygen which makes it one of the last of the minerals to form during the cooling of magma (melted rock beneath the surface of the earth, lava is magma at the surface). These veins can also intrude into non-igneous rock formations nearby. Quartz is extremely resistant to chemical weathering and as a result much of the sand we see at the beach is quartz reduced to the size of sand by mechanical weathering. These beautiful veins were part of a large formation of veins exposed in Chapman Creek, they occur alongside feldspars, also one of the final minerals to form from cooling magma.

Fold Lines & Intrusive Igneous Rocks

This picture shows darker bands of igneous rock intrusions into a larger rock mass, both undergo plastic deformation whereby the rock layers are folded and deformed as they are ductile; brittle rocks would fracture under the stress. Sites like this are extremely common in BC on exposed rock faces because BC is a very young (geologically speaking) mountainous area formed from the subduction of oceanic plates beneath the North American plates producing volcanism as well as the accretion of lithospheric (land) microplates (probably remnants of old plates) onto the North American plate, forming the western edge of the North American continent. As a result there has been much geologic deformation throughout BC.

Silt & Clay Layers of an Old Lakebed

Layers of silt and clays are sure signs of an ancient lake in the area, clays and fine silt will only settle out in a lake where there is little turbulence in the water keeping them suspended. This was likely the remains of a temporary glacial lake. BC was once almost entirely covered by glaciers (excluding only some coastal regions), glacial lakes would have been very common, especially around 10,000 years ago when the ice age ended and the glaciers melted. This photo was taken on the edge of Chapman Creek near sea level, and it had dozens and dozens of individual bands each signifying different, probably seasonal, depositional events.

Creekbed Layers

This layering effect is produced when creeks move and continue to gouge out the ground below. The layer of rounded rocks were smoothed by running water and deposited in the creekbed, then the creek continues to erode the land beneath it producing layers of rounded rocks now out of the water. The layer of fine sand in between was likely formed at the edge of the creek as it wandered in another direction. The creek is now forming a new layer of large rounded boulders in its new creekbed.

Glacial Deposits

Land Shaped By Ice: Like the rest of Canada, most of BC, excluding only low lying coastal areas, was covered by ice up until 10,000 years ago when the last ice age retreated from the land. It left behind glacial erratics, large pieces of bedrock moved far from their origin, as well as multitudes of glacial till - unsorted debris, irregular chunks of broken rock, sand, pebbles, and clay - left at the edges and front of a retreating glacier. You can tell the difference between glacial till and stream deposits because none of the rocks will have smooth edges and they will be unsorted -- there will be rocks of all sizes, as shown in the pictures at left.

These photos were taken at low-middle elevation on the back side of Mt. Elphinstone where there were large deposits of glacial till – unsorted debris left as the mountain glaciers retreated.

Granitic Igneous Rocks

Granite is the most common intrusive igneous rock body, commonly found at convergent plate boundaries where mountain-building events are occurring, hence are a very common site in BC. This is a fairly coarse-grained granitic rock, the right one consisting almost entirely of potassium feldspars and quartz, with the left one containing much more quartz. The large rock mass was recently exposed at the edge of a logging road and has been undergoing extensive mechanical weathering as the coarse crystals separate, one ‘rock’ sitting on the ground actually crumbled to hundreds of tiny pieces when I touched it.

Basaltic Igneous Rocks

Basalt is the most common extrusive igneous rock there is since this is what the oceanic plates are mostly made of, as are many island chains such as Hawaii and the Aleutian Islands. Basalt results from the cooling of ferromagnesium rich (mafic) magma at or near the surface resulting in a very dark fine grained rock that may/may not contain vesicles (air pockets) resulting from gases trying to escape. BC contains lots of basalt from both volcanism resulting from the subduction of oceanic plates and the accretion of oceanic plates. Gabbro is a coarse grained mafic igneous rock that forms from magma beneath the surface.

Iron Pyrite AKA Fool's Gold

Isometric, usually cubic crystals with parallel striations on faces, also found in nodules and massive formations. Brassy yellow in colour, often mistaken for gold, hence the common name Fool’s Gold. Streak is greenish black, hardness 6-6 1/2. Composed of iron and sulphur mostly, often with some nickel and cobalt. It is a widespread sulphur mineral, found in granite and syenite pegmatites, carbonatites, in blue schists in metamorphic rocks, mesothermal and epithermal veins, and in hydrothermal replacement deposits. Iron pyrite is an important source of sulphur and sulphuric acid, iron also produced from the process as a byproduct. This specimen was found in crushed rock that was used to create a new logging road, I never did find the original source of it.

Limestone

Description: Dense, fine grained rock, often so dense that a microscope is needed to view crystal structure. Fossiliferous limestones have textural patterns produced by the presence of fossils. Readily soluble in normally acidic rainwater producing caves of all sizes. Precipitation of solubilized limestone yields numerous cave forms such as stalactites, stalagmites, fracture fillings and crystalline sculptures. Usually white or light grey in colour, or darker when there is organic material (fossils) present. Yellow and brown forms are also occasionally found due to the presence of iron oxides. Hardness 3-4, easily scratched with a knife. Composed of 50% or more calcite, with various impurities composing the rest.

Environment: Occurs in beds from a few centimetres to 30m thick, also found in moundlike masses formed from fossilized reef structures.

Varieties: Clastic limestones are composed of broken shells, calcite and limestone fragments, formed from beach deposits. Chemical limestones are formed from precipitates in warm seas, hotsprings and limestone caves. Coquina is a pale brown limestone that is highly porous composed of marine or freshwater mollusc shells. Chalk is a white, soft and porous dense limestone formed from shells of microscopic organisms deposited in shallow marine water. Oolitic limestone is a warm shallow sea water deposit, often formed as inland seas rose up and dried out due to tectonic shift. Travertine is a colour-banded limestone formed in caves and hot springs. Organic or biogenic limestones are formed from coral, algal or foraminiferal deposits.

Notes: This is a photograph taken at the limestone caves near Homesite Creek.

Natural Spring Water

Far Left: A natural ephemeral (temporary) spring in a small valley in a limestone area filled with small caves and underground streams. This was during the spring snow melt when the water table was much higher than usual and all the ephemeral streams were flowing. April 2005 photo near Homesite Creek, BC.

Close Left: A natural spring at the base of a steep rock cliff, artesian wells are common where the land dips suddenly in elevation. Fall 2002 Photo near West Sechelt, BC.

About The Geoligical History of BC

Most of BC was formed in the last 200 million years by plate tectonics since the break-up of the super continent Pangaea when the Americas were still joined to Eurasia and Africa. 200 Million years ago there was no land west of where the Rockies are today, the land ended at Alberta, there were no Rocky Mountains either. Then as Pangaea split up and the plates continued to move remnants of sea floor and island chains were thrust up into the where the Rockies are today causing massive deformation and mountain building where the plates collided, as a result the sedimentary rocks at the edge of the continent were thrust upwards to form the Rocky Mountains. Over the course of the next 200 million years more and more pieces of sea floor and island chains were thrust up onto the continent while other pieces of sea floor were subducted hundreds of kilometres below the surface under the continent where it was then melted yielding magma which periodically came to the surface in a massive volcanic eruption, producing the beautiful Cascade Range Mountains on BC’s coast. It BC then it is not at all uncommon to find completely unrelated rock masses of different ages lying next to or on top of each other. Indeed, a geologic map of rock formations in BC, something we have only begun to map out in any detail, shows that BC is much like a jigsaw puzzle of intrusive & extrusive (volcanic) igneous rock formations, sedimentary rocks, sea floor, and pieces of islands that were swallowed up by the continent many millions of years ago.

Much more recently, from a geological perspective, BC has also undergone massive deformation as the result of a series of glacial and interglacial periods throughout the Pleistocene Epoch. During this period of time at least 12 glacial advances occurred where continental and alpine glaciation covered almost all of Canada, leaving only some small coastal islands free of ice. Each glacial period is triggered by a complex series of events including plate movement, climate change, alteration of oceanic currents, as well as solar cycles of the sun and minor cyclical irregularities in the earth’s rotation and orbit. These events allow snow to accumulate more in the winter and melt less in the summer, causing glacial advance. Glacial retreats were often relatively sudden, occurring over just a couple of thousand years, where the similar but opposite conditions to those that cause advance suddenly cause glaciers to melt more in the summer than they can grow in the winter. The last glacial retreat began about 14 000 years ago and BC was free of glacial ice, in all but the taller mountains, by about 11 000 years ago.

When the glaciers retreated they left behind a changed land in this province. Glaciers gouged out our mountain valleys creating beautiful jagged majestic horns (mountain peaks that are very jagged are caused by glaciers) and arêtes (sharp ridges between valleys), and between arêtes were the cirques, bowl shaped depressions where snow accumulates to form glaciers under favourable climatic conditions. Glaciers also left behind masses of sediments of ground up rocks and sand, characteristic U-shaped and hanging truncated valleys, striations and grooves gouged into bedrock, outwash planes and kettle lakes from their melt water, and they completely altered rivers, creeks and lakes from whatever may have been there originally. When the glaciers sat on this province sea level was 100m lower than it is today so that glaciers also gouged out the deep fjords, deep coastal valleys now filled with seawater, that cover much of BC’s coastline today. BC was also depressed by about 250m and parts of it are still undergoing isostatic rebound (uplift after the removal of the weight of the ice) today. This caused areas of BC’s coast to be under water as the sea level rose before the land did, further altering the face of BC’s coast.

Glaciation also had a profound effect on the evolution of flora and fauna in BC. BC, and indeed Canada, was covered in ice, a land barren of life. When the glaciers retreated 11000 years ago the recolonization of BC was blocked from the east by the Rocky Mountains so that necessarily most of our species had to come up from the south and are therefore direct descendants of southern species. These species, now separated from their southern counterparts continued down their own evolutionary path to become new unique species of their own. Further isolation caused by mountain ranges, rivers, and deserts within BC led to further speciation to produce the enormously biodiverse province we have today including many endemic species found no where else in the world.

BC then is a land of constant geologic change that has produced a land teeming with unique biological diversity.

Geological Features of BC today and the Geologic History of BC