I Geologic erosion Takes place without human influence Erosion is the The Great Leveler Sedimentary Metamorphic and Igneous Rocks Sedimentary and metamorphic rocks now cover 85 of land surface Underlain by igneous rocks A Sedimentary rocks B Metamorphic heat and pressure Marble metamorphosed limestone Slate metamorphosed shale Quartzite metamorphosed sandstone Schist flakes of mica Gneiss banded and elongated grains Alluvium material deposited by water Colluvium gravity Glacial till by glaciers Loess silty by wind Sandstone cemented sandy alluvium Shale clayey material compressed Limestone CaCO3 C Igneous Rocks Subdivided according to mineral composition and grain size Basalt Granite Quartz 1 III Elevated land Lava flows Uplift Deposition water lower than source Deposition wind higher than source Residual material Colluvial loose deposits usually in the footslopes carried by gravity Residuum loose weathered bedrock remaining essentially in place Water deposits Recent alluvium material deposited by a stream in comparatively recent time Beach deposits material deposited near the shore line of a lake Lacustrine deposit fine textured mostly finer than medium sand mineral material deposited in a lake environment Water deposits con t Organic deposit organic material peat and muck deposited in a lake Also included are related deposits such as comprogenous earth marl Outwash stratified coarse textured material mostly coarser than medium sand deposit by meltwater streams beyond active glacier ice 2 Water Deposits Water Deposits con t Beach ridges may occur singly or as a series of approximately parallel deposits Bog a former lake filled with peat muck marl or coprogenous earth Esker a serpentine ridge composed of stratified sand and gravel Formed by streams on or within the decaying glacier ice When the ice melts the stratified stream deposits are left as a ridge shaped landform Alluvial fan a low cone shaped deposit formed by material deposited from a tributary stream of steep gradient flowing into an area with less gradient Beach ridge an essential continuous ridge of sandy material behind a shore line that has been heaped up by wave or wind action Water Deposits con t Flood plain the nearly level lowest part of a valley which has been built from sediments deposited by the stream in Holocene recent time and subject to periodic flooding 3 Water Deposits con t Kame a conical hill composed of stratified sand and gravel It is formed where streams within the glacier ice deposit their load of debris Lake plain a level landform on the bed of a former lake composed of stratified material Water Deposits con t Outwash plain a large nearly level area not confined in a river valley composed of stratified materials deposited by melt waters from glaciers The soils on outwash plains are similar to those on river terraces Water Deposits con t Terrace landform in a stream valley below the upland and above the flood plain consisting of a nearly level surface and a hillslope leading downward from that surface like the tread and riser of stair steps 4 Water Deposits con t Terrace materials were deposited on the flood plains of streams when they carried large volumes of glacial meltwater Subsequently lift them as terraces which seldom or never flood Ice Deposits Glacial till nonsorted nonstratified sediment deposited glacier ice Ice deposits con t Drumlin wedge shaped mound of glacial till with clay core Glacial ice rides up over the top of a clay core from a lacustrine deposit The side closest to the advancing ice is steepest Often sits out in shallow lake and surrounded by sand and gravel 5 Ice deposits con t End moraine an accumulation of glacial drift built by the direct action of glacier ice Kettle a closed depression in glacial drift till or outwash made by the wasting away of a detached mass of glacier ice that had been either wholly or partially buried in the surrounding material Kettles are sometimes called pot holes Ice deposits con t Till plain glacial till deposits having a surface with low relief and gentle slopes In swell and swale topography the relief pattern is random The surface may be covered with loess but it is considered a till plain if the shape of the landform is controlled by the till surface and soil development extends into the till Till plain Flat a surface with very little relief Flat till plains are usually on till deposits of Illinoian age Swale the concave lower lying surface in swell and swale random very gently rolling topography on Wisconsinan age till deposits Soils in swales are usually darker and more poorly drained than the adjacent soils on swells Till plain con t Swell the convex higher lying surface in swell and swale topography on Wisconsinan age till deposits Soils on swells are usually lighter in color and better drained than the adjacent swale soils 6 Wind deposits Eolian sand wind blown sand Loess eolian deposits consisting mainly of silt Wind deposits Loess hillslopes landforms in windblown silt deposits that are thick enough for an entire solum to develop in loess IV Geomorphology Study of the Earth s surface forms and of the processes that shape them constitutes the field of geomorphology Sand dune mound ridge or hill of wind blown sand IV Geomorphology con t Structure physical nature and arrangement of rocks Stage landscapes youth maturity old slope Process combined action of agents building and eroding Climate weathering 7 Land forms Landforms are described as erosional those carved by running water or constructional those formed by depositional processes Erosional landforms have an open system of drainage in which the drainageway is open at one end and part of the recent sediment may be carried from that system Land forms Constructional landforms may have an open or a closed system a drainage system with no surface outlet in which the eroded debris is trapped within the system Land forms Erosional land form see next slide Upland head slope the concave portion of a slope at the head of a drainageway on which slope lengths converge downward Land forms Upland side slope the linear portion of a slope along the side of a drainageway Interfluve the high area between adjacent drainageways Slope profile components Slope profile components are represented by a side view of a hillslope Shoulder the convexly rounded component below the summit Backslope the linear part of the slope 8 Slope profile components con t Footslope the concave lower part of the slope