What are two agents of physical weathering that might occur in the mountains in northern Montana?
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1. Exfoliation caused by pressure release (tectonic)\n2. Exfoliation caused by temperature changes (heat/cold) \n3. Freeze-thaw (water)\n4. Abrasion (wind)\n5. Biological (trees, plants)\n6. Glacial plucking (gravity driven with freeze/thaw)
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temperate or deciduous forest- forest or mountain environment
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Signs of scraping on the rocks as the glaciers went by.\n\nShallow lakes left behind (tarn lakes, kettle lakes and Pater Noster lakes)\n\nGlacial till, or material pushed by the glacier like a bulldozer and then left behind in mounds. These mounds are called moraines.
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carnivore-cougar, weathering-whirlwinds, ecosystem-environment, erosion-earthquake (not very near) ?
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Generally sandstones and quartzites are more weathering resistant. They tend to form mountains and ridges. Limestones and shales tend to weather more and form valleys. They can't hold a mountain up. \n\nDifferential weathering is where different formations or even bedding within the same formation, weather at different rates. Softer, less competent rocks weather faster than harder, more substantial rocks. Look at a road cut, some rocks stick out like massive sandstones, and underlying shales have weathered back into the hillside. The rocks have experienced the same weathering forces, but the shales have weathered faster. Look at a cross-bedded sandstone. Some bedding is prominent and sticks out, some has eroded back in the formation. Both are differential weathering.\n\nIn the big picture, the rocks on a mountain have resisted weathering, where the rocks in the valley floor have succumbed, Differential weathering.\n\nThe last part of your question; think of a cemetery. Which gravestones last the longest? Lots of pink granite ones, huh? Granite is a very hard metamorphic rock. It is the most resistant to weathering. Marble is metamorphosed limestone. Much harder than limestone, but still CaCO3 (Calcium Carbonate). Rain is slightly acidic, so marble will weather out, but very slowly. Sandstone is a sedimentary rock, softer than granite or marble. So there is your answer.\n\nI hope this helps.
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Water\n\nSplash erosion is the detachment and airborne movement of small soil particles caused by the impact of raindrops on soil. Sheet erosion is the result of heavy rain on bare soil where water flows as a sheet down any gradient, carrying soil particles. Where precipitation rates exceed soil infiltration rates, runoff occurs. Surface runoff turbulence can often cause more erosion than the initial raindrop impact. Gully erosion results where water flows along a linear depression eroding a trench or gully.\n\nValley or stream erosion occurs with continued water flow along a linear feature. The erosion is both downward, deepening the valley, and headward, extending the valley into the hillside. In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is relatively steep. When some base level is reached the erosive activity switches to lateral erosion which widens the valley floor and creates a narrow floodplain. The stream gradient becomes nearly flat and lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion by far the most erosion occurs during times of flood, when more and faster-moving water is available to carry a larger sediment load. In such processes, it is not the water alone that erodes, suspended abrasive particles, pebbles and boulders can also act erosively, as they traverse a surface.\n\nWind\n\nWind erosion, also known as eolian erosion is the movement of rock and/or sediment by the wind. Windbreaks are often planted by farmers to reduce wind erosion. This includes the planting of trees, shrubs, or other vegetation, usually perpendicular or nearly so to the principal wind direction. The wind causes dust particles to be lifted and therefore moved to another region. Wind erosion generally occurs in areas with little or no vegetation, often in areas where there is insufficient rainfall to support vegetation. An example is the formation of sand dunes, on a beach or in a desert.\n\nGlacial\n\nIce erosion is caused by movement of ice, typically as glaciers. Glaciers can scrape down a slope and break up rock and then transport it, leaving moraines, drumlins and glacial erratics in their wake, typically at the terminus or during glacier retreat. Ice wedging is the weathering process in which water trapped in tiny rock cracks freezes and expands, breaking the rock. This can lead to gravity erosion on steep slopes. The scree which forms at the bottom of a steep mountainside is mostly formed from pieces of rock broken away by this means. It is a common engineering problem, wherever rock cliffs are alongside roads, because morning thaws can drop hazardous rock pieces onto the road.
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Englacial debris.\n\nThis debris is eventually deposited and forms a moraine.
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Mountains are either volcanic or tectonic.\n\nVolcanoes:\nThere are several processes in Plate Tectonics that cause volcanism, but they result in two main types of volcanism.\n\nVolcanism in subduction is caused by volitals, like H2O, CO2. These are carried down by the plate, mainly in the form of weak minerals. These minerals break down with pressure and temperature into stronger minerals that don't contain water and carbon dioxide. The leftover gases and liquids travel into the mantle (the mantle wedge) and hydrate the mantle, causing melting. The melt rises and then... volcano!\n\nThe other main cause is from rising mantle material, which forms decompression melting. Basically, hot mantle is kept from melting by the pressure of the earth at depth. When this material rises, the pressure drops much faster than the temperature, and thus it partially melts. This mainly occurs at divergent boundaries and hot spots, which are areas in plate tectonics that have rising materials or spreading.\n\nMountain Belts:\n\nNon-volcanic mountain belts are caused by compressive stress in plate tectonics. This can be 1. fold and thrust belts in highly compressive subduction zones (almost always from oceanic beneath continental subduction, e.g. east Andes, Rockies) or 2. continental-continental collisions (e.g. Himalaya, Appalachian).
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Mountains... I currently live in southern Colorado and it seldolm rains.  I am studying to be a geologist and find the physics required to create these moutain belts fascinating.
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Dust and sand is picked up from the soil as the wind passes over it.  It's more common to pick up dust and sand when:\n1) it's a deforested area with easy 'soil access' like a desert or plains (it doesn't happen in forests, or on grasslands);\n2) the soil exposed is dusty, sandy, or contains many small particles which can become windborne (it doesn't pick up gravel, or mud);\n3) the wind speed is high.\n\nI don't know exactly about 'abrasion' and 'weathering'.  in common usage, I'd say 'weathering' is ther main category which refers to changes in an object's surface in response to exposure.  Wethering can be caused by UV exposure (sunlight), acid rain, etc etc.  Abrasion is only caused by physical rubbing across things: sandstorms, rivers, etc.  Abrasion is IMHO a subset of weathering.
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Chemical erosion (also called weathering) occurs when rock or other materials are changed into smaller pieces by chemical processes.  These processes include direct oxidation (such as iron rusting), chemical dissolving (such as acid rain reacting with marble or limestone) and other chemical processes.  \nSome good site to look at are below:
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Decomposed rock and organic matter.
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My guess is dissipation, hydrothermal, volcanic. Just guessing.
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Basically anything eroding via dissolving.  A cave is a great example.\n\nRust and potholes are NOT chemical weathering.  Rust is a chemical change, but nothing is going away.  Potholes are mainly mechanical (cars do the eroding).
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I think there is some over-generalizing going on here. \n\nThe short answer: Granite is going to be more susceptible where its crystalline grain structure can be attacked by mechanical weathering. Limestone is going to be more susceptible where its softness is a disadvantage to mechanical weathering. For many types of mechanical weathering there is going to be little difference. \n\nHave you ever been to Yosemite? Half Dome, in the famous photographs by Ansel Adams is a perfect example of exfoliation of granite in sheets. This is a mechanical weathering process related to pressure release. Granite might be more susceptible to this (I am speculating) but only because it is often being unburied from much greater depths. Jointing in limestone is often related to pressure release. \n\nTo answer this question properly you need to consider the different types of mechanical weathering. I will compare the ones I can think of.\n1. Exfoliation caused by pressure release:  From my own field observations in areas where glacial unloading has occurred I would say that this affects both granite and limestone in a similar manner. Both will break off in sheets or blocks. \n\n2. Exfoliation is caused by temperature change: I have no quantitative proof but my opinion based on observation is that limestone is less susceptible to this because it is held together by cement and internal porosity probably has some ability to absorb differential expansion. Granite on the other hand is composed of crystalline grains that have different expansion rates and are likely to split apart. \n\n3. Freeze-thaw: Limestone does have bedding planes, and often has jointing as well, that is susceptible to this.  Some limestone has open porosity that also will be subject to some freeze expansion. Probably limestone is more vulnerable to this. Granite is going to be slightly susceptible to this only to the extent that water can penetrate it or to the extent it has been jointed or weakened by exfoliation. \n\n\n4.  Abrasion: Wind erosion affects both limestone and granite. Limestone is softer so windblown sand grains are more likely to erode the limestone. \n\n5. Salt-crystal growth: This is very common in coastal settings and sometimes in desert settings where moisture in the air is likely to contain some salts. Many of these salts will expand as the moisture that carried them evaporates. Heat will also cause them to expand.  I would say that granite is again more susceptible because of its crystalline grain structure. However, there is a special situation for limestone that few people who have never been in a cave have ever observed. Limestone often contains small deposits of anhydrite within the limestone. Anhydrite is unstable under surface pressures and tends to absorb water becoming gypsum. It expands as it does this and causes the limestone to break, often in sheets, but sometimes in blocks.  In many caves this is a primary cause of ceiling collapse and it can even result in stoping (raising the ceiling of the cave upward). \n\n6. Trees, plants: I doubt that there is any difference here. Some granite might provide more nutrients from chemical weathering to plants than limestone does, and so encourage its own destruction by plant roots, but both rocks are going to be susceptible. \n\n7. Tectonic and regional jointing: Tectonic events can cause fracturing in both types of rock. Limestone might be more flexible and be less susceptible to fracturing from mild folding. Regional jointing is related to pressure release and depends more on the burial and unroofing history than the type of rock. I don’t think either one is going to be more or less susceptible in most situations. Limestone often exhibits joints that can be traced for tens of miles that are related to regional stress regimes (both shear and extensional) and I believe that granite will produce similar joints.  You might be surprised to learn that the shear strength of granite and limestone are very similar
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What you are observing is the oxidation and weathering of a rock. The outside of the rock is exposed to the elements and gets bleached out, the inside is protected by the outer layers.
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Mountains are produced by forces in the earth that cause parts of the earth's crust to rise while others sink. Uplift of the crust, combined with chemical and physical erosion by air, water, and ice over millions of years, produces the spectacular scenery found in mountains. \n\nAt the very high temperatures and pressures found miles below the earth's surface, rocks can actually flow when density differences are produced by differential heating and cooling of parts of the mantle and lithosphere (Figure 1). The flowing of rocks in the mantle and lithosphere subjects parts of the crust to tension (pulling apart), while other parts are subjected to compression (squeezing together). Rocks are relatively weak and brittle under tension and, consequently, crust under tension tends to break up into giant blocks. Rocks are stronger under compression but when the compressive forces get very large, rocks deform by flowing, folding, and breaking.