She has done it again. She got me to look at this page by saying our island got pushed up here from somewhere south of the equator. I thought we might be able to make it back down there by January or February when the rain here gets really depressing. Now she tells me the island moves at about the speed my toe nails grow and so there is not a chance.....but look at what she has been up to. I just read the index here and I need a nap. Definitely a page reserved for the true fanatic! If you are a sensible, moderate dog like me click on my banner and read my no nonsense version of how this all happened.

1. What you would expect to find
2. Observation that do not coincide with expectation.
3. How they determine the age of rock.
4. How they determine where rock was formed.
5.  Recently developed theory to explain formation of the Western Cordillera and Vancouver Island.
6. How the terrane known as Wrangellia, which makes up the main part of Vancouver Island, was formed.
7. How two more terranes were added to give Vancouver Island its present character.
8. A table showing the geological history of Vancouver Island.
9. A glossary of some of the technical terms used.
10. Further reading

The links marked with asteriks (*) are internal links that will take you to a definition of the term in the glossary at the bottom of this page.

Now I have explained why we might expect those layers to be uplifted at strange angles because of folding action. Something like this then would be readily explained using the simple theories previously described.

The mountains of the Rockies are formed of blocks of sedimentary rock which have been thrust up and folded. Moving to the west these are followed by ranges of mountains made of granite, the next ranges are of volcanic shale or of severely metamorphosed rocks, then there are some composed of unaltered limestone, then granite again, followed by a range of volcanics and deep-water shale. Some of the limestone formations contain the remains of organisms identical to those found in the tropics. Geologists were faced with the prospect of trying to explain how this limestone with its tropical fossils had ended up amidst a broad mountain belt in the Northern temperate zone. The rock on Vancouver Island shows similar variations from one location to another. They were formed at different times and in different places or at least that is what geologists would have us believe. How did they arrive at that conclusion?

*Geochronology is the dating of rock by measuring the naturally occuring radioactive isotopes in the minerals to see how far they have progressed in their change to their base element. Uranium and thorium are radioactive isotopes that, in time, are converted into a "daughter" mineral, lead. Potassium-40 decays to become Argon-40. From laboratory experiments, scientist have been able to determine, in years, the length of time this transformation takes. By determining the progress of the radioactive decay of these isotopes their age, and the age of the rock formations they were part of, can be determined.

 Along the east shore of Buttle Lake there are several outcrops of black volcanic rock which have holes drilled in them. These are small core holes that were drilled by Ted Irving, a geoscientist of the Geological Survey of Canada . Tropical varieties of fossils had been found in the limestone formations near the top of this formation which suggested that these and the older rocks beneath them had not always been part of North America. Irving and an associate Ray Yole, collected several drill-core samples along the shores of Buttle Lake and subjected them to detailed laboratory testing. Their results suggested that 230 million years ago, the Karmutsen Formation of Vancouver Island was formed far to the south. It was pieces of information like this that led to the development of a theory to explain how the Cordillera Region, including Vancouver Island, were formed and became part of North America.

On a previous page we have given a simple explanation of the theories of plate tectonics and continental drift. A full explanation of the formation of Vancouver Island requires further elaboration on the information provided there.

 In the 1950's and 1960's oceanographers and geologists began mapping the ocean floors. They found deep trenches and mid-oceanic ridges . This led to the formation of a theory based on sea-floor spreading and plate tectonics as a modern expression of the old idea of contintental drift. The crust that forms the floor of the ocean is constantly being created along the global mid-ocean ridges and then being consumed in the subduction zone. We have already mentioned that there is a subduction zone just off the west coast of North America. As new crust is made and old crust is destroyed the pieces of the earth's crust are moved from one place to another. In time these pieces of crust carrying volcanoes or coral-lime stone reefs bump into a continent and are welded to it. These pieces of crust that have joined on to other land masses with differing geological histories are called *terranes.

This map of British Columbia shows the terranes that make up the Western Cordillera. Laurentia is the original North American Continent. The other terranes have come in from distant locations like huge rafts of rock and been plastered on to the continent causing the wide sedimentary plains of the original continent to be thrust upward to form the Rockies. The add on terranes each bring with them their separate history.

 As these mountains were raised, they were exposed to the forces of erosion and rock, sand, silt and clay were washed from them into nearby basins. On the western coast of the island in the region of Quatsino Sound this gave rise to the Coal Harbour Formation. About 85 million years ago the basin on the east coast which had received a substantial run off of eroded silt and gravel from the newly uplifted mountains developed into a swampy area which supported a heavy growth of vegetation. The plants of this ancient forest, collapsing into the swampy low lands, were transformed into coal deposits and this coal and the sedimentary rocks eroded from the surrounding mountains gave rise to the Nanaimo Formation.

This chart summarizes the history of the geological formation of Vancouver Island. The links in the right hand column are to representations of the area referred to on a map of the island.
 
 

Era and Period	Geological Activity	Resulting Formations
Paleozoic Era Upper Devonian Period 380 million years ago	The region that makes up Wrangellia started in this era as a broad ocean lava plain. An arc of volcanoes became active. These were of the explosive variety and sent forth ash, blocks of lava and volcanic sandstone.	The Sicker Group of Volcanic and Sedimentary Rock was formed at this time.
Paleozoic Era Carboniferous and Permian Periods 360 to 245 million years ago	Volcanic action ended and the action of wind and water eroded the island arc to form an underwater plateau. Colonies of shelled sea animals contributed their shells of calcium carbonate to form limestone	The Buttle Lake Formation was created.
Mesozoic Era Triassic Period 208 to 245 million years ago.	Towards the end of this period an underlying ocean crust split apart and magma oozed up through the fractures and spread outwards. This lava is chemically different from that found from the earlier eruptions. The rock formed from it is black basalt.	The Vancouver Group was created. It is comprised of the Karmutsen and Quatsino Formations.
Mesozoic Era Jurassic Period 135 to 208 million years ago	During this period arc volcanic action began again in Wrangellia. This was different than the volcanic action of the Devonian period. Lavas were ejected on land and magma deep beneath the earth's crust cooled slowly to form gneiss. The great batholiths were formed.	The Island Intrusions and Bonanza Group were created by this volcanic activity.
The Mesozoic Era, Cretaceous Period 65 to 140 million years ago.	It was during this period about 100 million years ago that Wrangellia crashed into North America. This collision resulted in crushing, folding and faulting of the colliding terranes. Mountains were formed and about 85 million years ago a broad basin formed on the east coast of the island. There were low swampy areas filled with rich vegetation which was later transformed into coal	The Leech River Formation was added and the Nanaimo Formation was created.
The Cenozoic Era, Paleogene Period 65 to 21 million years ago	The Pacific Rim Terrane probably originated from large submarine land slides in the area where the modern Juan de Fuca Islands are located. During this period it moved up to their present location. About 42 million years ago the Crescent Terrane which is composed of ancient sea floor volcanic rock was thrust up against the Pacific Rim Terrane and pushed under it. This pushed the Western and Southern Edges of Wangellia up into the air where erosion began wearing away the rock.	The Metchosin Volcanics, Catface Intrusions and Carmanah Group were created during this period.

• antclinorium

A large upwarped structure, several kilometers in width and length consisting of many lesser folds.
• biostratigraphy

is the dating of sedimentary rock by refference to the fossil forms found in it.
• fault

a fracture in the earth along which, rocks on one side of the fracture have moved relative to rocks on the other side.
• fold

warped or bent strata. If the strata is bent upwards, it is called an anticline, if it is bent downward, it is called a syncline.
• geochronology

is the dating of rock by calculating the rate of decay of radioactive isotopes within the rock.
• inclination

The amount of inclination from the horizontal of a vertically orientated dip needle. At the poles the inclination is 90 degrees.
• magnetometer

A device for measuring the strength and direction of the earth's magnetic field. Specialized forms of magnemeters are used to measure the remnant magnetism in ancient rocks.
• terrane

parts of the earth's crust which preserve geological records which differ from those of neighbouring terranes.

Bibliography

• The Geology of Southern Vancouver Island, A Field Guide. by C.J Yorath and H.W. Nasmith. Published in 1995 by the Pacific Section , Geological Association of Canada. Orca Book Publishers, Victoria, B.C., Canada.
• West Coast Fossils by Rolf Ludvigsen and Graham Beard, published in 1994 by White Cap Books, Vancouver and Toronto.