TOPOGRAPHIC RELIEF PHYSICAL GEOGRAPHY: An overview Prof. Anthony Grande AFG 0913 2 Definitions GEOLOGIC PROCESSES Geography: Study of people living on the surface of the earth. Geology: the study of the earth and its processes. Geomorphology: the study of landforms. Topography: the study of surface features. 3 TECTONIC (building) Folding Faulting Volcanism NATURAL PROCESSES Mass movements Earthquakes Volcanic eruptions Subsidence GRADATIONAL (wearing down) Weathering: mechanical and chemical (in place) Mass wasting (by gravity) Agents of Erosion (with movement: take-move-place) - Running water - Moving ice - Wind - Wave action - Long shore currents 4 Folding Faulting Folded rock layer in the Catskills. Forces at work: Compression, bending, breaking 5 Lake Champlain, Lake George Forces at work: movement, and Sacandaga Lake are in rift tension, breaking 6 valleys (also called grabens). 1
New England Seismic Network including NYS Earthquakes occur throughout NE United States and SE Canada. - Two major clusters in eastern NY. - One minor cluster in western NY. Zones of Seismic Activity in NYS 3. CLARENDON- LINDEN ZONE 1. LAURENTIAN ZONE Earthquakes are caused by adjustments to the earth s surface (rebound) as tension is released. 7 2. RAMAPO ZONE Source: NYS Museum 8 NE US Earthquake Hazard Zones Volcanism least 1 greatest 3 2 9 Forces at work: melting, movement of molten material, explosive 10 There are 3 categories of rocks, each formed differently, each with different resistances to erosion: Sedimentary Igneous Metamorphic Watkins Glen State Park, Tompkins Co. Sedimentary Rocks formed by the compaction of eroded material from other rocks or precipitates from dissolved minerals under pressure from the weight of successive layers. They make up 75% of the earth s surface. Watkins Glen State Park, Tompkins Co. 11 12 2
Sedimentary Rocks Sediments are laid down in horizontal layers. The layers are then often deformed d by folding and faulting or displaced by volcanic activity. Helderberg Escarpment Hudson Valley Lowland Cliff face Catskills They are eroded by running water. in Ausable Chasm, Essex Co. 13 14 Igneous Rocks formed by the cooling and solidification of molten material. The rate of cooling determines its crystalline structure. The rate of cooling determines the creation of minerals. Igneous Rocks Igneous rocks are found at the surface in: (1) SE NYS from Staten Island to Rockland Co. along the Palisades sill. (2) NE NYS in the Saratoga Springs area where there are hot springs and pillow lava formations. (Pillow lava is a formation created when molten rock hits cool water.) (3) The Hudson Highlands and Adirondacks contain Pre- Cambrian igneous rock. 15 16 Palisades Sill Igneous Rocks Pillow lava at Stark s Knob, NY >> Below, recent pillow lava underwater off of Hawaii. Sill: a horizontal underground lava flow intruded between layers of sedimentary rock. 17 <<Volcanic sill, Haverstraw, NY (Rockland Co.) related to the Palisades formation. 18 3
Metamorphic Rocks formed by the addition of great heat and pressure to existing sedimentary, igneous and metamorphic rocks. For example, shale (sed.) becomes slate sandstone (sed.) becomes quartzite limestone (sed.) becomes marble granite (ign.) becomes gneiss basalt (ign.) becomes schist. Metamorphic Rocks Metamorphic rocks are found in eastern NYS (Taconic Mts., Hudson Highlands and the Manhattan Prong), the Adirondack Mts. and in the Thousand Island region (Frontenac Arch). Frontenac Arch (Thousand Is) Adirondacks Taconic Mts. Hudson Highlands Manhattan Prong 19 Banded gneiss in Adirondacks. 20 Resistance of Rocks Setting of Niagara Falls The composition of the rocks give them the ability to resist forces of erosion. Igneous and metamorphic rocks are generally stronger. They are resistant to erosion and form highlands. Sedimentary rocks tend to be weaker. They are found in lowlands. Together they give us a variety of surface features and slope angles. 21 The Niagara River drains Lake Erie. It flows over the Niagara Escarpment to reach Lake Ontario. In doing so for 12,000 yrs, it has created a 7 mile long gorge as the falling water eroded weak layers of rock. Lake Erie 22 miles upstream of the Falls. Moved 7 miles GORGEin 12,000 yrs 9 miles from escarpment 16 miles from the Falls 22 Niagara Escarpment Retreat of Niagara Falls At the present rate of erosion it will take the Niagara River 75,000 years to reach Lake Erie. << Each layer of rock has a different resistance to water erosion. 23 24 4
Niagara Falls Niagara Falls American Falls 2011 1969 www.dailymail.co.uk/news/article-1338793/niagara-falls-ran-dry- Photos-moment-iconic-waterfall-came-standstilll.html - photos of dry Niagara Falls in 1969 25 Horseshoe or Canadian Falls 26 Genesee River Letchworth State Park 27 Genesee River in the Grand Canyon of the East. 28 High Falls on the Genesee River at Rochester Present Geology of NYS Generalized Geology Detailed Geology 29 THE GEOLOGY OF NYS IS VERY COMPLEX 30 5
Detailed Geologic Map of NYS Hot links to the fold out map that comes with the Geology of New York State book: http://geology.about.com/library/bl/maps/n_statemap_ny3100.htm http://geology.about.com/library/bl/maps/n_statemap_nyexplan.htm Bedrock Geology and Surface Landform Features of NYS 31 32 Terrain Units 1. Mountains 2. Plains 3. Hills 4. Plateaus 5. Coasts NYS is unique in that all major landform units are found within its borders. Elevations within NYS Elevations range from 0 ft (sea level) along the shores of Long Island and the Hudson estuary to 5,344 ft at Mt. Marcy in the Adirondacks. 33 34 Landscape Characteristics Areas of Excessive Slope 35 From Thompson, Geography of New York State 36 6
Cross-sections Climate Regions of NYS Appalachian Plateau S N Tug Hill/AdirondacksW E W S Catskills N E 37 38 System of Rivers and Lakes as part of the physical landscape Landscapes of NYS Land + climate provides the basis of lakes, rivers, soil and scenery. It is a finite resource, one that cannot be manufactured by people. >>PHYSICAL LANDSCAPE People manage it and reap its harvest: crops, forest products, wildlife and minerals. People tend to concentrate their settlement on the best lands: flat with fertile soil, ease of construction, fresh water supply and access to transportation routes. >>CULTURAL LANDSCAPE 39 40 7