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GROUNDWATER

GROUNDWATER. WEATHERING AND EROSION. Geologic work of groundwater. Groundwater dissolves rock Groundwater is often mildly acidic Contains weak carbonic acid Forms when rainwater dissolves carbon dioxide from the air and from decaying plants

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GROUNDWATER

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  1. GROUNDWATER WEATHERING AND EROSION

  2. Geologic work of groundwater • Groundwater dissolves rock • Groundwater is often mildly acidic • Contains weak carbonic acid • Forms when rainwater dissolves carbon dioxide from the air and from decaying plants • Carbonic acid reacts with calcite in limestone to form calcium bicarbonate, a soluble material

  3. Geologic work of groundwater • Solution channels – network of dissolved channels through limestone • Caverns • Most caverns are created by acidic groundwater dissolving soluble rock at or just below the surface in the zone of saturation • Features found within caverns • They form in the vadose zone

  4. Geologic work of groundwater • Caverns • Features found within caverns • Composed of dripstone (travertine) • Calcite deposited as dripping water evaporates • Collectively, they are called speleothems • Includes stalactites(hanging from the ceiling) and stalagmites (form on the floor of a cavern)

  5. Speleothems in Carlsbad Caverns National Park

  6. “Soda straws” in Carlsbad Caverns National Park

  7. Geologic work of groundwater • Karst topography • Landscapes that to a large extent have been shaped by the dissolving power of groundwater • Some common features include • Irregular terrain • Sinkhole or sinks (formed by groundwater slowly dissolving the bedrock often accompanied by collapse) • Striking lack of surface drainage (streams)

  8. Development of karst topography

  9. Development of karst topography

  10. Hot springs and geysers • Hot springs • Water is 6-9oC warmer than the mean annual air temperature of the locality • The water for most hot springs is heated by cooling of igneous rock • West – closeness to volcanic activity • East – deep circulation of water – geothermal gradient

  11. Hot springs and geysers • Geysers • Intermittent hot springs • Water erupts with great force • Occur where extensive underground chambers exist within hot igneous rock • Groundwater heats, expands, changes to steam, and erupts

  12. Distribution of hot springs and geysers in the United States

  13. Old Faithful geyser in Yellowstone National Park

  14. Hot springs and geysers • Geysers • Chemical sedimentary rock accumulates at the surface • Siliceous sinter(from dissolved silica) • Travertine (from dissolved calcium car-bonate)

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