The Mountains Come Down – Breaking Down the Rocks

The Mountains Come Down – Breaking Down the Rocks Name: __________________________________________________ Period: _____ Date: ____________ Essential Question: How do mountains shrink? As we look upwards, it's hard to imagine the mountains almost twice their present size – however in their infancy they were almost that large. Slowly, through the processes of weathering and erosion, the mountains have been reduced to a fraction of their original size. The material removed or eroded from these mountains has been used to help fill in the many lakes and deltas in the area. This will all lead to a very different terrain in a few dozen million years from now. How are the Mountains Slowly Shrinking? Chemical Weathering -many of the rocks that make up the mountains, in particular limestone, are susceptible to chemical reactions with materials carried in the air and water. The water dissolves the limestone and other rocks forming Karst topography or underground cave. The most common types of chemical weathering are oxidation, hydrolysis and carbonation. Chemical weathering is fastest in warm climates. Physical weathering process of rocks breaking apart without changing their chemical composition. Examples of physical weathering are freeze and thaw or frost wedging and exfoliation. Freeze and Thaw - water is unique. As it freezes, it expands in volume. In the mountains, snow melts during the day, and the resulting water flows into cracks in rocks. Overnight, as temperatures drop, the water expands and freezes. This expansion provides an incredible wedging force that break rocks Glaciation - glaciers take the landscape and sculpt it. Sharp v-shaped valleys are smoothed into rounded u-shaped valleys. Gravity plays a major in glaciations. Avalanches - as snow accumulates high in the mountains, eventually gravity take over and the excess is released in the form of avalanches. Running Water - water is the king of erosion. Nothing carves up a landscape like the action of water. Soil Creep - very subtle, creep can be almost undetectable. It is normally found on weathered mountain slopes. Under the force of gravity, the material slowly begins to slide downhill, and eventually the signs of creep become evident. Slumping - in many situations, a steep hillside will show a spoon-shaped depression within which the material has begun to slide downhill. Rockslides - sometimes, as layers of rock are steeply uplifted, the bonding of one layer to another may be weakened by the action of water or other agents of erosion. As the force of gravity constantly pulls down on the surface of a steep slope, there may eventually be a failure. As a fracture occurs at the top, a layer may slide down suddenly creating a large rockslide. Wind- wind blows away sediment. In areas where the wind constantly blasts, as in the Bow Valley, the wind may add to the effects of other forces. Sand dunes form because of wind erosion. Wind is the greatest agent of weathering and erosion in the desert. Biological Action -the orange and green lichens that coat many of our rocks are slowly breaking them down. Lichens are composite organisms consisting of a fungus and a photosynthetic partner growing together in a symbiotic relationship. Clarifying questions: 1. Why are mountains shrinking? Sinkholes form in areas with soluble bedrock like limestone. Water dissolves the rock, creating underground voids. Eventually, the overlying soil collapses into these voids, forming a depression on the surface. ___________________________________________________________________________________________________ 2. What happens to the materials eroded from the mountains? Materials eroded from mountains can be transported by rivers, wind, or glaciers and deposited in valleys, plains, or oceans. ___________________________________________________________________________________________________ 3. What is Karst topography? Karst topography is a landscape formed from the dissolution of soluble rocks like limestone, characterized by features like sinkholes, caves, and underground drainage systems. ___________________________________________________________________________________________________ 4. How do caves and sinkholes form? Caves form through the dissolution of limestone by acidic groundwater, while sinkholes form when the roof of an underground cavern collapses. ___________________________________________________________________________________________________ 5. How can freezing and thawing break rocks? Freezing and thawing can break rocks through the expansion of water as it freezes in cracks, exerting pressure and causing fractures. ___________________________________________________________________________________________________ glaciers, which sculpt the land through processes like plucking and abrasion. 6. Glaciation is erosion by _____________________________________________________________________________ snow, ice, and debris that rapidly slide down a slope. 7. Avalanches are made up of _________________________________________________________________________ The "king of erosion" is often considered to be water, due to its ability to wear away rocks and reshape landscapes through 8. What is the king of erosion? _________________________________________________________________________ processes like erosion and weathering. Soil creep is caused by the gradual downhill movement of soil due to factors like gravity, expansion and contraction from freezing 9. What causes soil creep? ____________________________________________________________________________ and thawing, and the action of roots. Slumping is a type of mass wasting where a mass of rock and soil moves downhill along a curved surface, often due to saturation with water 10. What is slumping? ________________________________________________________________________________ or undercutting. 11. What is a rockslide?A______________________________________________________________________________ rockslide occurs when a mass of rock rapidly moves downhill along a steep slope due to factors like gravity, weathering, or seismic activity. Sand dunes form through the accumulation and movement of sand grains by wind, typically in desert or coastal environments. 12. What causes the formation of sand dunes? ___________________________________________________________ are symbiotic organisms composed of fungi and algae or cyanobacteria, which can grow on rocks and contribute to their weathering 13. What are lichens? Lichens ________________________________________________________________________________ through chemical processes like acid secretion. __________________________________________________________________________________________________ Use Venn diagram to show the similarities and differences between glaciations, avalanche, soil creep, and rock slide. Matching Type: B ____ 14. Chemical Weathering C ____ 15. Physical weathering E ____ 16. Freeze and thaw H _____ 17. Glaciation G _____ 18. Soil creep F _____ 19. Slumping D _____ 20. Wind A _____ 21. Biological action A. lichens produce a weak acid that breaks down rocks B. oxidation, hydrolysis and carbonation C. exfoliation and frost wedging D. forms sand dunes E. water expands when it freezes causing rocks to break F. a spoon-shaped depression G. materials, soil and rocks, slowly to slide downhill H. glaciers sculpt the land Research: How do sinkholes form? Sinkholes form through a process called karstification, where water dissolves soluble bedrock like limestone, creating underground ________________________________________________________________________________________________ voids. Over time, the unsupported surface layers collapse into these voids, forming sinkholes. Factors like heavy rainfall, changes in groundwater levels, and human activities can contribute to their formation.