Erosion & Deposition by Water Formation of Landforms by Streams & Erosion and Deposition by Groundwater, Waves, and Currents 3.3 & 3.4
Main Ideas • Describe the role of stream erosion and deposition in building landforms • Describe the effects of erosion by groundwater • Describe how erosion and deposition by waves and currents shape shorelines
Formation of Landforms by Streams(some landforms result from stream erosion) • Streams erode soil and rock to form channels • Over a course of many years, the erosion of sediment from the bottoms of the channels may cause canyons and valleys to form • Oxbow lakes form when a bend in a stream is eroded on its outer sides and deposits sediment on its inner side causing a sharper bend – eventually the bend becomes cut off from the main stream as the stream forms a new channel
Formation of Landforms by Streams (other landforms result from stream deposition) • Floodplain: area of deposited sediment caused by flooding • Alluvial fan: forms as a stream slows down, spreads out and deposits sediment • Delta: forms at the mouth of a rivers; as a stream enters and ocean and slows, sediment is deposited in a fan shape.
Erosion and Deposition by Groundwater, Waves and Currents • Groundwater erosion can change the land – can erode rock, forming underground caverns or spaces. The roof of a cavern may fall, producing a sink hole • Waves and currents can cause shoreline changes and land formations – wave action against coastal rock causes many formations – sea cliffs, headlands, sea caves, sea arches, and sea stacks. • Beaches, sandbars and barrier islands are formed and destroyed by erosion and deposition by waves and currents.
“Take Away” from lesson • Stream erosion plays a part in the formation of channels, oxbow lakes, valleys and canyons • Floodplains, alluvial fans and deltas are formed by deposition of stream sediment • Groundwater erosion may cause underground caverns and sinkholes to form • Erosion and deposition by waves and currents cause many shoreline formations • Shoreline erosion and deposition depends on the hardness of the rock and wave energy
Homework • Read pgs 32 – 38 and answer following questions on a separate sheet of paper – • 13 • 14 • 18 • 20 • 21