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Download Title Page Photo “Come forth into the light of things, —William Wordsworth
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Title Page Photo “Come forth into the light of things, Let Nature be your teacher.” —William Wordsworth Solution Processes and Karst Topography The Impact of Solution Processes on the Landscape Solution and Precipitation Caverns and Related Features Karst Topography Hydrothermal Features The Impact of Solution Processes on the Landscape • Underground Water – Slightly Acid (e.g. carbonic acid – H2CO3) – Dissolves certain rock-forming chemicals, especially calcium and magnesium carbonates • Effects of Solution on the Landscape – Karst topography – Hydrothermal surface features Karst Topography (Rolling landscape and sink holes) Solution and Precipitation • Dissolution – Process of going into solution – Solubility varies among different elements Most soluble in H2O Least soluble in H2O – Fig . 17-1 Solution and Precipitation • Example of dissolution: Carbonate Rocks – They are common rocks and highly soluble Dissolution (breakdown of minerals) → Solution (salts dissolved in water) CaCO3 calcium carbonate + H 2O water + CO2 carbon dioxide CaMg(CO3)2 + dolomite 2H2O water + 2 CO2 → carbon dioxide → Ca(HCO3)2 calcium bicarbonate Ca(HCO3)2 + Mg(HCO3)2 calcium magnesium bicarbonate bicarbonate • Role of Bedrock Structure – Joints becomes solution pathways – Network of solution tubes widen to form small rooms and large caverns (large rooms) – Fig. 17-2 Caves and Related Features • Location – Usually found where there is massive limestone bedrock, and plentiful underground water • Formation: Two-stage process – Initial excavation stage by solution action – “Decoration stage” by precipitation of minerals • Speleothems: e.g., stalagmites, stalactites, and pillars – Fig. 17-4 Caves and Related Features – Precipitate formations • Speleothems – Decorative features formed from deposits – Precipitated mineral deposits are usually calcite. – On walls, roofs, floors of caves (a) – E.g., flowstone on cavern ceiling (a) and wall (b), Lost River Caverns, Hellertown, PA (Richard A. Crooker photos) (b) – Fig. 17-3. Speleothems such stalactites hang from the ceiling of this room in New Mexico’s Carlsbad Caverns. Some of them have joined with stalagmites to form pillars. You’ll find similar formations in the Mammoth Cave National Park, Kentucky. Karst Topography • ‘Karst’ – Ancient Slavic word (Germanized), meaning “barren land” – Name of Karst region of the former Yugoslavia with this kind of topography • Topography – Rugged hilly area shaped by solution of limestone (sometimes contains dolomite, gypsum, or halite). See next slide. – Fig. 17-5. Namesake karst region of former Yugoslavia. – Extent: 10% of Earth’s land area has soluble carbonate rocks at or near surface. In the U.S. lower 48 states, it’s 15%. Limestone leads to Karst Regions. – Fig. 17-6 *Notable in Karst Landscapes are the absence of surface streams. They’re sometimes “lost rivers”. See next slide. Lost River Cave & Valley, Bowling Green, Kentucky Spring • Surface features – Early development: sinkholes (or dolines) and disappearing streams (a.k.a. “lost rivers”). – Fig. 17a – Advanced development: sinkholes (or dolines), collapse dolines, and uvala (chain of intersecting sink holes). – Fig. 17b – Tower Karst (late development): haystack hills (mogotes) and exposure of non-soluble bedrock – Fig. 17-7c – Fig. 17-8. Tower karst in Guilin, China. • Sinkholes as Natural Hazards – Fig. 17A. This sinkhole swallowed a house in central Florida. Precipitation Processes – “Precipitation” in this sense, means the elements recombine, and are removed from water and deposited. Here, it has nothing to do with “rain”. – Caves, geysers and hot springs encourage these deposits, as the pressure in caves drop, or as temperatures drop around the lip of a hot spring. • In caves, air pressure is lower than in joints and bedding planes. • In geysers and hot springs, air pressure drops suddenly, and there is also rapid heat loss to air. Think of the mineral ‘ring’ that is left behind in a pot when you boil water. – Fig. 17-12. Geyser with a nozzle in Yellowstone National Park, Wyoming. Hydrothermal Features • Hot Springs – Eject hot water – Source is volcanic heat and pressure – Calcium carbonate precipitates when water reaches surface – Calcium carbonate deposits could be: • Travertine (massive) • Tufa (porous) – Fig. 17-9 – Carbonate terraces accrete around hot springs – Fig. 17-10. Hot spring atop a carbonate terrace in Yellowstone National park. Algal growth highlights the spring. – Travertine terraces (hot spring is on top of terrace and out of view) – Fig. 17-17. Mammoth Hot Springs, Yellowstone National Park, WY; Fig. 17-16 • Geysers – A hot spring that is intermittent – Usually hot water ejects (erupts) sporadically instead of flowing continuously. It’s a temporary eruption that reverts to dormancy, and then the cycle starts again – Shoots up into the air; this eruption releases pressure build-up within a restricted subterranean tube. – Fig. 17-11. Old Faithful geyser in Yellowstone National park. • Fumaroles – Unlike a geyser, very little water drains into the tube of a fumarole – It’s a hot spring that lacks water; it sends out only steam – Fig. 17-13. • Yellowstone National Park, Wyoming – America’s showcase of hydrothermal features – Fig. 17-15. Yellowstone National Park and its major geyser basins.
