{"id":188,"date":"2014-06-13T19:41:09","date_gmt":"2014-06-13T19:41:09","guid":{"rendered":"http:\/\/opentextbc.ca\/geography\/?post_type=chapter&p=188"},"modified":"2015-07-21T11:27:27","modified_gmt":"2015-07-21T18:27:27","slug":"9-4-geology","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/geography\/chapter\/9-4-geology\/","title":{"raw":"Geology","rendered":"Geology"},"content":{"raw":"The term geology<\/strong> comes from the Greek words \"ge\" (\"earth\") and \"logia,\" meaning the study of and\u00a0discourse involving the\u00a0solid Earth, including the rocks of which it is composed, and the processes by which those rocks\u00a0change. Geology can also refer generally to the study of the solid features of any celestial body (such as the Moon or Mars).\u00a0Geology gives insight into the history of the Earth by providing the primary evidence for plate tectonics, the evolutionary history of life and past climates<\/a>.\r\n\r\n<\/a>In British Columbia, geology is\u00a0important for economic development associated with mineral and hydrocarbon (oil and natural gas) exploration and\u00a0harvest. Geology is valuable to the public for predicting and understanding natural hazards, the remediation of environmental problems, and for providing insights into past climate change. Geology also plays a role in geotechnical engineering and is a major academic discipline.\r\n\r\nFormation of the\u00a0mountains is a dramatic evolving process associated with geology and\u00a0geomorphology<\/strong>. Geomorphology is the study of the process that creates and transforms the surface of the Earth.\u00a0Geomorphology seeks to understand landform history and dynamics, and predicts changes through a combination of field observation, physical experiment and numerical modelling (geomorphometry).\r\n\r\nThe Earth is stratified, meaning that it has several layers. In the very centre lies the solid core, which\u00a0is surrounded by a liquid core. Next is the mantle, asthenosphere, the lithosphere and finally the crust at the top.\r\n\r\n[caption id=\"attachment_822\" align=\"aligncenter\" width=\"400\"]\"Firgure<\/a> Figure 8.6 Earth cutaway from core to crust, the lithosphere comprising the crust and lithospheric mantle (detail not to scale)[\/caption]\r\n\r\nEach of these layers is made up of different mineral composition.\r\n\r\nSeveral types of rocks are found throughout the crust. Plate tectonics theory suggests that the Earth\u2019s lithosphere is made up of seven large plates and several small ones. Rising convection plumes from the asthenosphere can force the plates to move. The plate edges are\u00a0where most volcanic and earthquake activity take place. These activities move minerals and materials. Below is a map of the geologic era rock found in British Columbia.\r\n\r\n[caption id=\"attachment_186\" align=\"aligncenter\" width=\"400\"]\"Figure<\/a> Figure 8.7. Geologic era of rock in British Columbia[\/caption]\r\n\r\nPlate tectonics is a significant field of study in BC since as there are so many fault lines (see Figure 8.8). Faults are where plates meet. When two plates jam together, the edges often fracture and collapse\u00a0forming mountain ranges in a process called\u00a0orogeny<\/strong>.\r\n\r\nAnother significant process to the formation of the rugged terrain found in BC is\u00a0isostasy,<\/strong>\u00a0which is the process of the surface of the Earth loading and unloading. For example, the Rocky Mountains are made up of sedimentary rock which erodes relatively quickly.\u00a0 A process is known as\u00a0isostatic rebound<\/strong>, occurs which is the gradual rising of land elevations as it springs back after thousands of years of being crushed under the weight of continental glaciers.\r\n\r\nA complex system of fault lines can be found in British Columbia. In Figure 8.8,\u00a0all known and inferred fault lines are present with\u00a0the major fault lines\u00a0in bold. These fault lines\u00a0have been designated as \"major\" because of their length and their\u00a0potential impact on human populations.\u00a0The five fault lines featured in the figure\u00a0are the Pinchi Fault in Central BC, the Fraser River Fault, the Columbia River Fault, the Rocky Mountain Fault and the San Juan Fault.\r\n\r\n \r\n\r\n[caption id=\"attachment_187\" align=\"aligncenter\" width=\"400\"]\"Figure<\/a> Figure 8.8 British Columbia fault lines[\/caption]\r\n

Subduction<\/h2>\r\nView a short video on subduction from the National Oceanographic and Atmospheric Administration at http:\/\/oceanexplorer.noaa.gov\/edu\/learning\/player\/lesson04.htm<\/a><\/span>While the San Juan Fault\u00a0may look small on this map, an earthquake along this fault could have significant ramifications for the residents of southwestern BC.\u00a0The San Juan Fault separates the oceanic Juan de Fuca Plate from the heavier and denser\u00a0North American continental plate through subduction<\/strong>. Subduction<\/strong> occurs when two plates collide and one is denser or heavier than the other, forcing the heavier one downward and under the other.\u00a0 Subduction can cause trenches in the ocean floor, which will warm and may cause the plate to melt, producing magma and flow into volcanic eruptions at the surface resulting in new rocks. These processes also move and transfer minerals and sediment from different layers of the Earth and deposit them in different places.\r\n\r\nUnderstanding how and where these pieces of sediment have come from and moved to help geologists unlock the mystery of\u00a0 the formation of surface terrain. For example, the\u00a0Pinchi Fault is a significant fault system in central BC that\u00a0extends 450 kilometres and separates dominating oceanic sedimentary bedrock in the region from the volcanic rocks\u00a0 in the eastern portion of the province (Plouffe, 2001). The\u00a0 resulting\u00a0terrain consists of\u00a0a plate pushing up instead of down against the edge of the neighbouring plate, which\u00a0can cause significant earthquakes.\r\n

Attributions<\/h2>\r\n