Chapter 16 Landscape Evolution: Geomorphology Topography is a Balance Between Erosion and Tectonic Uplift 1 Topography is a Balance Between Erosion and Tectonic Uplift 2 Relief • The relief in an area is the maximum difference between the highest and lowest elevation. – We have about 7000 feet of relief between Boulder and the Continental divide. Relief 3 Mountains and Valleys • A mountain is a large mass of rock that projects above surrounding terrain. • A mountain range is a continuous area of high elevation and high relief. • A valley is an area of low relief typically formed by and drained by a single stream. • A basin is a large low-lying area of low relief. In arid areas basins commonly have closed topography (no river outlet to the sea). Mountains • Typically occur in ranges. • Glaciated forms –Horn –Arête • Desert Mountains – Vertical Cliffs – Alluvial Fans 4 Mountain Landforms: Horn Deserts: Vertical Cliffs and Alluvial Fans 5 Valleys and Basins • River Valleys – U-shape (Glacial) – V-shape (Active Water erosion) – Flat-floored (depositional flood plain) • Tectonic (Fault) Valleys (Basins) – Tectonic origin – San Luis Valley – Jackson Hole – Great Basin U-shaped Valley: Glacial Erosion 6 V-shaped Valley: Active water erosion Flat-floored Valley: Depositional Flood Plain 7 Desert and Semi-arid Landforms • A plateau is a broad area of uplift with relatively little internal relief. • A mesa is a small (<10 km2)plateau bounded by cliffs, commonly in an area of flat-lying sedimentary rocks. • A butte is a small (<1000m2) hill bounded by cliffs Plateau, Mesa, Butte 8 Colorado National Monument Canyonlands 9 Desert and Semi-arid Landforms • A cuesta is an asymmetric ridge in dipping sedimentary rocks as the Flatirons. • A hogback is ridge formed by near- vertical, resistant sedimentary rock. (Dakota Ridge) • Badlands are areas of deeply gullied topography unsuitable for agriculture. Cuesta 10 Hogback Bad- lands 11 Landform Terms • Relief • U-shaped • Mountain Valley • Mountain • V-shaped Range Valley • Valley • Plateau • Basin • Mesa • Horn • Butte • Arête • Cuesta • Alluvial Fan • Hogback • Badlands 12.