Geology includes the study of the earth’s crust, its structure, the chemical composition and the physical properties of its components. Rock formations are located within the crust, their formation is studied and measurement is made of the forces that create, bend and shape mountains, basins, faults, volcanoes and earthquakes. Geology also examines the erosion of rocks and the deposition of the loose materials. It also reveals the physical history of the Earth.
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A geological province is an extensive region with distinctive characteristics that differentiate it from surrounding areas. A shield is a large area of very ancient rocks that have been leveled by erosion. A platform is that part of a continent covered by flat-lying or gently tilted rock and underlain by very ancient rocks consolidated during deformations that preceded deposition of the overlying platform layer. The rocks of the platform layer are usually sedimentary in nature. An orogenic belt is a part of the continent where the Earth’s crust has been subjected to deformation leading to the creation of a mountain range. Finally, a continental shelf (or continental platform) represents the extension of a continent under an ocean. It is characterized by a very gentle slope and generally reaches depths of less than 200 metres, at which point there is a steep slope down to the ocean floor.
Age of Rocks
The geologic time scale divides the 4.6 billion years of earths history into hierarchy of time periods. Every layer of rock corresponds to a specific time in the history of the formation of the Earth.
The Precambrian era began with the formation of the Earth; it was followed by the Paleozoic, Mesozoic, and Cenozoic eras. Each of these eras is divided into periods, the periods into epochs, and epochs into ages. Paleontological studies and isotopic dating methods are used to determine the time divisions.
Canadian Geochronology Knowledgebase
The compilation represents publicly available geochronological information for Canada, with data compiled from federal, provincial and territorial government publications and reports, university theses, books and journal articles.
Major Rock Categories
Rocks are divided into three main categories according to how they were formed: igneous, sedimentary or metamorphic processes. Rocks differ in their texture, mineral and chemical composition, and bedding characteristics depending on which of these three processes that formed them.
Igneous rocks, which are also referred to as magmatic rocks, are formed from materials that come from the depths of the Earth. There are two categories of igneous rocks: intrusive (or plutonic) rocks and volcanic rocks.
Sedimentary rocks are the product of the consolidation of loose sediment that has accumulated in beds.
A metamorphic rock is derived from a pre-existing igneous or sedimentary rock that is transformed, to a greater or lesser degree, by the action of physical factors such as temperature and pressure, or chemical factors that include the addition of new minerals.
Location of Kimberlites (1997)
Kimberlites are rock formation where diamonds can be found. Diamonds form at a depth greater than 150 kilometres within the earth. After their formation, diamonds are carried to the surface of the earth by strong volcanic activity. This mixture of magma, transported rock and diamonds forms pipes called kimberlites as it reaches the surface.
Contained within the 4th Edition (1974) of the Atlas of Canada is a map showing geological age and lithology accompanied by a supplementary map at a scale of 1:50 500 000, displaying geological provinces.
Surficial Materials and Glaciation
Most unconsolidated materials covering the Canadian landmass have glacial origins.
Some sediments were entrained by glaciers and deposited at a distance without being sorted. Other sediments were picked up and reworked by glacial melt water, or transported and deposited by river or wind action. Some sediments are organic or volcanic in origin. Sediments are classified according to the manner in which they were transported and deposited.
Contained within the 4th Edition (1974) of the Atlas of Canada is a map that shows the successive stages in the retreat of the last ice sheet in North America in respect to coverage of the Canadian landmass.
Included with the map are the speculative ice-marginal positions with approximate time in years before present and present day ice cover which is denoted as well as areas which were unglaciated during the last glaciation period.
Contained within the 4th Edition (1974) of the Atlas of Canada is a set of two maps. One shows the maximum post-glacial marine limit in feet above present sea level and the second shows the maximum height of post-glacial rebound in feet above present sea level.
Both maps show existing glaciers and are accompanied by a detailed text providing background information on the post-glacial marine limit, post-glacial rebound and the production of these two maps.
Canada’s landscape is very diversified and comprises several distinctive areas, called physiographic regions, each of which has its own topography and geology. The physical geography of Canada comprises two great parts: the Shield and the Borderlands.
The Shield consists of a core of old, massive, Precambrian crystalline rocks. The Borderlands areas are formed by younger rocks and surround the Shield like two rings. The inner ring comprises a chain of lowlands, plains and plateaus of generally flat-lying sedimentary rocks. The outer ring consists of discontinuous areas of mountains and plateaus in which the younger rocks are deformed. Each of these areas is divided into regions, each of which comprises many smaller subdivisions that are distinctive based on their topography and geology.
The map shows the location of these physiographic regions.
Permafrost occurs when the ground remains at or below a temperature of 0oC for a minimum period of two years. Permafrost occurs not only at high latitudes but also at high altitudes.
Almost all of the soil moisture in permafrost occurs in the form of ground ice, which in turn occurs in several different forms. The quantity of ice in the ground varies widely.
Permafrost and ground ice have had significant effects on the economic development of the North. It affects the energy and mining industries, as well as the construction of modern settlements and infrastructure elements such as roads, railways, airfields, and utilities.
Significant Earthquakes and Seismic Hazard
An earthquake is the rapid shaking of the Earth’s surface that follows the sudden release of energy within the Earth. They are most commonly caused by movements along the edges of the plates that make up the Earth’s crust. Each year, more than 3500 mostly small earthquakes are recorded in or near Canada, 50 of which can be felt. More than half of all the earthquakes in Canada occur along the west coast. There is also scattered activity in southeastern Canada and in the Arctic. The size of an earthquake is measured on a magnitude scale, and its intensity is measured on the Modified Mercalli Scale.
The map shows the most significant earthquakes recorded in Canada to 2006.
There are many geologically active volcanoes along the Canadian Cordillera in British Columbia and the Yukon. Recurrent earthquakes below our feet and gigantic mountain ranges rising majestically upward remind us that this part of Canada is geologically active. The possibility of an eruption, even a large explosive one, cannot be ruled out.
The map shows the major volcanoes and areas with significant accumulation of volcanic ash.
Space Weather - Geomagnetic Activity Zones
The magnetic field of the Earth is influenced by the electromagnetic environment of the solar system. The disturbed interplanetary environment changes the conditions of the natural electromagnetic environment of our planet and affects normal operation of space and ground technological infrastructures, such as power grids and pipelines. Geomagnetic activity can be described by the sizes of the disturbances in the Earth magnetic field and how often they occur. Geomagnetic activity depends on the geographic location of the observing point. It is defined by the geometry of the Earth’s geomagnetic field and its interaction with both the charged particles produced by the Sun and the solar/interplanetary magnetic field fluctuations.
Canadian territory covers three zones of geomagnetic activity: the polar cap (north of Cambridge Bay), the auroral zone (between Cambridge Bay and Meanook) and the subauroral zone (south of Meanook). The highest geomagnetic activity is observed in the auroral zone.
Space Weather - Telluric Activity Zones
The magnetic field of the Earth is influenced by the electromagnetic environment of the solar system. The disturbed interplanetary environment changes the conditions of the natural electromagnetic environment of our planet and affects normal operation of space and ground technological infrastructures, such as power grids and pipelines. The geomagnetically induced currents that directly affect vulnerable infrastructure are driven by the geoelectric (telluric) field.
Therefore, the most important task in space weather hazard mapping is to identify the areas with different levels of telluric activity. On the map, telluric activity is defined as the annual percentage of the time when variations in the activity is above the normal level of 20 milliVolts per kilometre. Elevated telluric activity occurs for a quarter of the year in the auroral zone, whereas it varies from 15% (4.5 times per month) down to just a few percent (1 occurrence per two months) in the Prairies. It is interesting to note that most of the big cities in Canada, and therefore much of the infrastructure, are in the least tellurically active zone (less than 10%).
Major Landslides Causing Fatalities
Landslides are the downslope movements of sediment and rock. They can be found in any part of Canada, even in areas with very little relief. They happen in bedrock or in loose sediment, on land or under water. They can be large or small, rapid or slow, and generally occur without warning.
The map depicts 45 landslides in Canada that have resulted in more than 600 fatalities in historical times (1840 - 2006).
A tsunami is a sea wave or series of waves produced by large disturbances of the sea floor that are of relatively short duration. Such disturbances cause the water column to move vertically and the resulting wave energy to spread outwards across the ocean surface at high speed. Although tsunami occurrences in Canada are rare, they do occur and can cause major damage and loss of life. Since the beginning of the twentieth century, there has been one tsunami reported about every fifteen to twenty years in Canada.
The map shows the location of the major tsunami events in Canada including earthquake and landslide events that triggered tsunamis.
Contained within the 4th Edition (1974) of the Atlas of Canada is a map that shows geologic structural features and denotes tectonic elements by a color-coding system. There are also descriptive elements and features of tectonic elements which are displayed.
Earthquakes, Magnetism and Tides
Contained within the 3rd Edition (1957) of the Atlas of Canada is a plate that shows maps of earthquakes, magnetism and tides across Canada.
The two larger upper maps on this plate show geomagnetism. Since the North Magnetic Pole is in a different position from the Geographical North Pole, and the lines of the earths magnetic forces are deflected by various agencies, the compass needle does not point toward the Geographical North Pole in most locations. The deflection of the compass needle from True North is called magnetic variation or declination. Thus, for example, where variation is west, north as indicated by the compass needle is west of True North by the number of degrees marked on the isogones, as illustrated by the upper left map on this plate.
The upper right map indicates the average annual change of magnetic variation in minutes. The small inset map at the top of this plate, entitled Earthquake Probability, shows the damage which may result from earthquakes occurring in different parts of the country. The zones are graded from 0, where such earthquakes are likely to do no damage, to 3, where earthquakes are likely to do major damage. The small-type numbers indicate the magnitude of some recorded earthquakes. The index of magnitude is related to energy released rather than the damage done. A magnitude 5.6 is considered as the threshold at which damage begins.
The four lower maps on this plate show co-tidal and co-range lines for/from the semi-diurnal and diurnal tides. A co-tidal line indicates the position of the crest of the tidal undulation at a given time. The hours marked on these lines are intervals in lunar time from that instant when the moon crosses the Greenwich meridian. A co-range line indicates the difference in level between the crest and the trough of the undulation.
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