Lecture 3 Flashcards
Endogenic vs. Exogenic Processes
Endogenic processes are responsible for creating topographic relief, i.e., variations in elevation of land surface relative to sea level.
ex:volcanism, earthquakes, and folding and faulting of rocks in the earth’s crust.
Exogenic processes operate to reduce topographic relief by means of weathering of rock and subsequent redistribution of weathering products, sediments and dissolved minerals, across the earth’s surface.
denudation.
The processes of weathering, erosion, transport and deposition are collectively referred
3 most common rock-forming minerals present in the earths crust are…
QFM
The three most common rock-forming minerals present in the earth’s crust are quartz (SiO2), which usually occurs as a six-sided prism, feldspar (NaAlSi3O8 ,CaAl2Si2O8), which occurs as a six-sided rhombus, and mica (K(Mg,Fe)3AlSi3O10(F,OH)2), which occurs as thin sheets of prismatic crystals. Rocks are defined as mineral aggregates.
Geologists arrange the rocks that compose the earth’s crust into three major classes:
Igneous rocks are derived from molten rock or magma, which originates beneath the earth’s crust.
Sedimentary rocks are derived from the weathering and erosion of pre-existing rocks or formed by chemical precipitation in aquatic environments, i.e., lakes and oceans.
Metamorphic rocks are formed of igneous and sedimentary rocks that have been changed physically and chemically by the application of heat and pressure during mountain building periods.
Igneous Rocks
name and describe two main types
1.ferromagnesian minerals:
Mafic igneous rocks consist largely of minerals composed of silicon and oxygen atoms combined with metallic elements such as iron (Fe) and magnesium (Mg).
-Oceanic crust consists largely of the mafic igneous rocks basalt and gabbro. Rocks of the oceanic crust exhibit an average density of 3,000 kg/m3.
2.aluminosilicate minerals
Felsic igneous rocks consist largely of minerals composed of silicon (Si) and oxygen (O) atoms, combined with a variety of metallic elements such as sodium (Na), potassium (K), calcium (Ca), magnesium (Mg) and aluminum (Al).
-The continental crust consists largely of granite, a felsic igneous rock, and gneiss, a metamorphic rock derived from granite. Rocks of the continental crust exhibit an average density of 2,700 kg/m3.
The crust is much thicker beneath ______ than beneath _______, approximately 40 km versus 5 km, respectively.
continents
oceans
Felsic vs.Mafic
- 2 main elements of both and other elements in both
- where are they usually found
Felsic:
- Felsic igneous rocks consist largely of minerals composed of silicon (Si) and oxygen (O) atoms, combined with a variety of metallic elements such as sodium (Na), potassium (K), calcium (Ca), magnesium (Mg) and aluminum (Al).
- continental plates
Mafic:
- Mafic igneous rocks consist largely of minerals composed of silicon and oxygen atoms combined with metallic elements such as iron (Fe) and magnesium (Mg).
- ocean plates
The continental crust consists largely of _____, a felsic ______ rock, and ______, a _______ rock derived from _____(same as first blank). Oceanic crust consists largely of the mafic ______ rocks _____ and _____.
granite,igneous
gneiss,metamorphic
igneous
basalt and gabbro
Sedimentary Rocks
Physical weathering serves to break down rock into smaller particles known collectively as clastic sediments. Physical weathering does not alter the chemical composition of the original rock materials. Chemical weathering transforms the original minerals (primary minerals) into a new set of minerals (secondary minerals) of different chemical composition and minerals dissolved in surface and ground waters.
clastic sedements
Physical weathering serves to break down rock into smaller particles known collectively as
Through a variety of processes known collectively as ________, sediment grains are welded together to form clastic sedimentary rocks. ________ (composed of gravel), _______ (composed of sand), and _______ (composed of mud) are examples of these rocks.
Through a variety of processes known collectively as lithification, sediment grains are welded together to form clastic sedimentary rocks. Conglomerate (composed of gravel), sandstone (composed of sand), and shale (composed of mud) are examples of these rocks.
What are organic rocks?
Organic rocks originate as organic materials produced by a variety of organisms, both terrestrial and aquatic. Fossil fuels such as coal, natural gas and oil are derived from the decomposition and subsequent transformation of organic materials by heat and pressure within the earth’s crust.
Metamorphic Rocks
Processes accompanying mountain building occur at high temperatures and pressures. Under these conditions igneous and sedimentary rocks are altered to form metamorphic rocks. Physical changes in rocks accompanying metamorphism involve the re-arrangement of mineral grains into parallel layers creating a mineral structure known as foliation. Gneiss (coarse texture; large mineral crystals) and schist (fine texture; small mineral crystals) are common foliated metamorphic rocks.
Physical changes in rocks accompanying metamorphism involve the re-arrangement of mineral grains into parallel layers creating a mineral structure known as _______. ______ (coarse texture; large mineral crystals) and ______ (fine texture; small mineral crystals) are common foliated metamorphic rocks.
foliation
Gneiss (coarse texture; large mineral crystals)
schist (fine texture; small mineral crystals)
Continental landmasses of the circumpolar North are divided into 3 main physiographic regions based on bedrock composition, geologic age and variations in topographic relief:
1) Continental Shields – Canadian Shield, Baltic Shield and Central Siberian Plateau;
2) Sedimentary Platforms – Interior Plains of Canada, Arctic Islands, excluding Devon, Axel Heiberg and Ellesmere Islands, East European Plain and West Siberian Lowland; and
3) Orogenic Mountain Belts – Western Cordillera of North America, Axel Heiberg and Ellesmere Islands among the Arctic Islands, Ural Mountains and East Siberian Highlands in Russia (Figure 3-1a).
Canadian Shield
The Canadian Shield represents the ancient core of the North American continent. The rocks that compose most of the Canadian Shield record several cycles of mountain building over several billion years. Extensive volcanism accompanied deformation and metamorphism of igneous and sedimentary rocks (Figure 3-1b). Granite and gneiss dominate the bedrock geology.
Torngat Mountains in Labrador and the Davis Highlands of Baffin are examples of…
Mountain ranges are located along the uplifted eastern margin of the Canadian Shield: the Torngat Mountains in Labrador and the Davis Highlands of Baffin, Devon and Ellesmere Islands (Figure 3-2b). These mountains have been eroded by glacier ice to create a fjord coastline.
clay belt
what is it and where is it?
South of Hudson Bay and James Bay, the Canadian Shield lies buried beneath a broad, flat clay plain known as the Clay Belt. The land surface in this region is characterized by the presence of poorly drained muskeg (Figure 3-2c). The Clay Belt originated at the end of the last Ice Age (9,000 to 8,000 years ago). Meltwater flowing from the Laurentide Ice Sheet created enormous proglacial lakes known as Glacial Lake Barlow and Glacial Lake Ojibway. Large volumes of silt and clay derived from the glacial erosion of bedrock were deposited on the floors of the proglacial lakes. Subsequent drainage of these lakes exposed the fine-grained sediments as clay plains creating extensive areas of low topographic relief.
Hudson Bay Lowland
The Hudson Bay Lowland is a vast, low-relief wetland called muskeg, which is composed of peat and other organic deposits. The wetland consists of a mosaic of ponds and lakes with forest patches occupying the slightly higher, better-drained parts.
2 biggest Orogenic Mountain Ranges in north
- Innuitian Province
- This region of northern Canada includes Axel Heiberg and Ellesmere Islands within the Arctic islands. This region experienced deposition of an immense thickness of sedimentary rocks over hundreds of millions of years (Figure 3-1b). An early episode of mountain building (approximately 540 to 360 million years ago) involved eruption of lava and folding and faulting of the overlying sedimentary rocks. Further uplift of the region was associated with emplacement of large volumes of granite within the crust. Subsequent weathering and erosion (approximately 360 to 66 million years ago) heralded the return of the deposition of great thicknesses of sedimentary rocks along the margin of the Arctic Ocean. Sedimentary rocks in the western region of the province give rise to low-lying terrain usually less than 600 metres above sea level. Sedimentary and igneous rocks in the eastern region form upland terrain more than 1,000 metres above sea level and glacier-capped mountains over 2,000 metres above sea level on Axel Heiberg and Ellesmere Islands (Figure 3-3). - Western Cordillera
- The terrain in this region is composed of a variety of igneous, metamorphic and sedimentary rocks (Figure 3-1b) that have experienced folding and faulting. The intrusion of large volumes of granite into the earth’s crust and eruption of lavas during construction of volcanoes have contributed to mountain building along the western coastline of Canada over the last two hundred million years. Alpine glaciation has created the rugged topography that characterizes much of this region (Figure 3-4). The highest peaks in Canada, Mount Logan (5,959 metres above sea level) and Mount St. Elias (5,489 metres above sea level), are found in this physiographic region.
- glacial troughs
- cirque
- arêtes
- parallel valleys
- bowl-shaped basin at the top of the mountain
- The morphology of the ridges separating adjacent glaciers (arêtes) is controlled by the structure of the tightly folded sedimentary rocks in the mountains
Sedimentary Platforms
Sedimentary platforms separate orogenic mountain belts from the Canadian Shield. The oldest sedimentary rocks, consisting of limestone, dolomite and shale, underlie the Hudson Bay Platform (Figure 3-1a). The Interior Platform is developed on sedimentary rocks consisting largely of limestone, dolomite, sandstone and shale (Figure 3-1a). The Arctic Coastal Plain is developed on gravel, sand and silt deposited along the coastline of the Arctic Ocean basin (Figures 3.5a and 3.5b).
Coastlines in the Canadian Arctic are presently at risk due to _______.
Coastlines in this region of the Canadian Arctic are presently at risk due to sea level rise. Rapid shoreline retreat is associated with melting ground ice and a longer ice-free season that contributes to enhanced wave erosion of coastline sediments
Tectonic plate margins diverge or move away from one another at _________
mid-oceanic ridges
The upward movement of magma through the crust causes the crust to fracture and facilitates eruption of lava onto the ocean floor to construct mid-oceanic ridges.
