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Chapter 1 Landform Patterns and Processes Topography · the natural and human features of the Earth’s surface. ie. Surface features · need to understand difference between relief and elevation Elevation - the height of a particular point of land above sea level Relief - the change in elevation over a given distance Hill · areas of high relief with elevations no higher than 300 - 600 m · isolated features Mountain · areas of high relief with elevations higher than 300 - 600 m · most occur in long linear chains called ranges (usually along margins of continents) Plain · a level tract of land · frequently found along coastal areas or at lower elevations · very gentle slope and no local a relief for thirty metres or more Plateau · an extensive, relatively flat upland area · have been raised upward into higher elevations by movements of the Earth’s crust · often found in interiors of continents · because they are often deeply eroded by stream valleys, they have more rugged appearances than plains Draw conclusions about patterns in major landforms on the earth’s surface. · figures on page 8 & 9 of text · reproducible worksheets 1.3 & 1.4 The Structure of the Earth · fill in details from page 5 of text on reproducible worksheet 1.1 Core · Inner Core · deepest part of the earth (1512 miles deep) · solid that contains both iron and nickel · is a magnet, a compass · Outer Core · (1419 miles deep) · similar to the inner core but it is a liquid (contains sulphur and oxygen which lowers the melting point) · Mantle · Occupying 1789 miles · magma (iron and magnesium) that makes up the mantle · mostly solid except the outer 200-300 Km which is extremely hot and goopy; very plastic-like · outermost liquid layer of the mantle is referred to as the asthenosphere Lithosphere (Crust) · the crust and that upper layer of the mantle which lies above the asthenosphere · basically hardened mantle (magma) · contains two segments, the oceanic and continental crusts Compressional force · a force pushing into a part of the earth’s crust, causing it to buckle · plates move towards one another, squeezing together · subduction zones sometimes form along these areas Tensional force · a stretching force in the earth’s surface which may cause faulting · plates break apart, moving away from or past each other, which may form a trench as one plate drops downward · ridge zones sometimes occur where two plates move apart. Magma may rise between the plates and form a ridge See figure 1.9 page 11 and figure 1.10 page 12 - discuss Discuss formation of volcanoes along ridges, etc. by looking at figures Mountain Building Fold mountains · an upland area formed by the buckling of earth’s crust. Many fold mountains are associated with destructive or collision margins of plates. · amount and extent of force and pressure, can create simple or complex forms. · Anticline · an arch-like upfold in buckled, bent, or contorted rock. · looks like the letter ‘A’ · Syncline · a downfold of rock layers. · looks like a ‘S’mile Mountains formed by faulting · Normal Fault · a fault in which rocks have moved down the slope of the fault · two normal faults occur parallel to each other, with plate in-between dropping down as plates move away from each other - forms rift valley · land between two parallel faults rises - forms block mountain · Reverse Fault · a fault, perhaps caused by a compressional force, where movement is up, rather then down, the face over which movement occurs. · Overthrust Fault · occurs when a plate that undergoes faulting has already experienced folding and its folded layers are then pushed up and thrust over layers on the faults other side. Mountains formed by Volcanoes · Along plate boundaries, heat is generated because of friction, pressure, and decay of radioactive materials. · Intense heat melts rock beneath the crust producing magma · If it reaches surface - through fractures or vents, extrusive volcanic activity takes place. · Terms · Lava - liquid rock · Ash (cinder) - small molten rock fragments · Vent - Single opening through which the volcanic products erupt Mild volcanic eruptions · thin, liquid lava flows · small amounts of gas Explosive volcanic eruptions · thick lava flows · large quantities of gas, ash and cinders · why? - thick lava hardens quicker - plugs up - and then must be exploded out Three types of Volcanic Cones Ash and Cinder Cone · eruptions consist mainly of ash and cinders · thick, slow flowing, rapidly solidifying lava · shape is symmetrical · steep sides · large crater Shield Cone · usually milder eruption · little or no ash and cinders · very thin, liquid lavas · broad, flat cones Composite Cone · undergoes periods of both explosive and quiet activity · layers of ash and cinders intermixed with layers of lava · weak spots may develop on sides with smaller lava flows forming smaller craters Reproducibly Worksheet 1.6 - Enlarge map part to full page Mark subduction zones and mid-oceanic ridges Page 16 question 16a and page 17 question 17a