Introduction to Geography Arthur Getis, Judith Getis, & Jerome D. Fellmann

Physical Geography: Landforms Chapter 3

Overview Earth Materials Geologic Time Movements of the Continents Tectonic Forces Diastrophism Volcanism Gradational Processes Weathering Mass Movement Erosional Agents & Deposition Glaciers Waves, Currents, & Coastal Landforms Wind Landform Regions

Earth Materials Igneous Rocks Sedimentary Rocks Metamorphic Rocks

Igneous Rocks Cooling & solidification of molten rock Underground molten rock is magma Above ground molten rock is lava Composition of magma & lava + cooling rate determines the minerals that form Granite, basalt, pumice, obsidian

Sedimentary Rocks Composed of particles of gravel, sand, silt, & clay Pressure & cementing processes cause rocks to form Large particles form conglomerates Sand forms sandstone Silt & clay form shale or siltstone Organic materials form limestone or coal

Metamorphic Rocks Formed from igneous or sedimentary rocks by earth forces that produce heat, pressure, or chemical reactions Shale becomes slate Limestone can become marble Granite may become gneiss

Geologic Time Earth formed 4.7 billion years ago Current landforms are often millions of years old Early 20 th century work by geologist Alfred Wegener on continental drift helped to explain how landforms developed over time

Movements of the Continents Plate tectonics theory Earth’s crust is outer, lighter portion of the lithosphere Lithosphere broken into 12 large and numerous small plates that slide & drift over the asthenosphere Plate movement may be caused by convection

Plate Boundaries Divergent plate boundaries Plates move away from each other Transform boundaries Plates slide by each other horizontally Convergent boundaries Plates move towards each other Plate collisions can cause earthquakes along faults

Convergent Movement Convergent plates can cause deep-sea trenches and continental-scale mountain ranges Heavy, but thin, oceanic crust tends to be forced under continental crust Deep trenches form at these subduction zones Volcanoes and earthquakes are common in subduction zones For example, the Ring of Fire

Tectonic Forces Diastrophism Great pressure causing plates to fold, twist, warp, break, and compress Volcanism The force that transports heated material to or toward the earth’s surface

Diastrophism Broad warping Folding Faulting Escarpments Rift valleys Tsunami

Volcanism Strato or composite volcano Steep sides Shield volcano Gentle slopes No explosion

Gradational Processes Reduction of the land’s surface Types Weathering Mass movement Erosion

Weathering Mechanical Frost action Salt crystals Root action Chemical Oxidation Hydrolysis Carbonation

Mass Movement “Mass wasting” Downslope movement of material due to gravity Accumulation of rock particles at the base of hills is talus

Erosional Agents & Deposition Running water Amount of precipitation Length & steepness of the slope Kind of rock & vegetation Forms landscapes such as deltas

Stream Landscapes Humid areas Waterfalls V-shaped channels Floodplains Meandering streams Oxbow lakes, natural levees, flooding Arid areas Lack of vegetation increases erosional forces Temporary lakes Alluvial fans Deep, straight-sided arroyos (wadi) Buttes & mesas

Groundwater Aquifers form in zone of saturation Upper zone is the water table Can dissolve soluble materials to form stalactites, stalagmites, & sinkholes Karst topography

Glaciers Covered a large part of the planet only ,000 years ago Large body of ice moving down a slope or spreading outward on a land surface Can move as much as 1 meter per day

Glacial Landforms Glacial troughs U-shaped valleys Fiords Tarns Cirques Arêtes Outwash plain Moraines

Waves, Currents, & Coastal Landforms Waves Deposition & erosion Sandbars Longshore currents Forms beaches & spits Coral reefs & atolls Formed by the secretion of calcium carbonate by coral organisms in sunny, warm water areas

Wind Abrasive action of sand & dust sculpts the landscape Dunes Barchan Loess

Landform Regions A large section of the earth’s surface where a great deal of homogeneity occurs