Weathering Processes PDF

Three Types of Rocks These are rocks that are formed from the solidification of molten rock material. These are rocks that formed through the accumulation, compaction, and cementation of sediments. These are rocks that form from the...

Three Types of Rocks These are rocks that are formed from the solidification of molten rock material. These are rocks that formed through the accumulation, compaction, and cementation of sediments. These are rocks that form from the transformation of pre-existing rocks through the process of metamorphism. ROCK CYCLE  It is a significant process that creates landforms and helps shape the earth.  Freeze-thaw weathering or Frost Wedging Exfoliation weathering or Unloading Thermal Expansion Abrasion and Impact Salt weathering or Haloclasty  Have you ever left a glass container of liquid in the freezer only to find it had broken? Ice forms in cracks in rocks and exerts pressure on the rock. Frost/Ice Wedging can cause potholes to form in pavement The outer layer of rock break away from the rest of the rock. Exfoliation- gradual peeling of layers due to uplift and frost action. Exfoliation of Igneous rock Some types of rocks form beneath the surface of the earth. This causes them to form under increased pressure than that of rocks that form on the surface. If something happens to cause the rock to come to the surface (like an earthquake), then the pressure is release and the rock will expand. As it expands, it pushes the outermost layers of the rock outward until they break off. Formed after glaciers caused surface rock to be removed. This released the pressure on rock under the surface and allowed it to expand, breaking off in sheets that slid off the side of the mountain leaving a half dome shape. CALIFORNIA, USA - OCTOBER 23: Half Dome view in Yosemite National Park of California, United States on October 23, 2022. (Photo by Tayfun Coskun/Anadolu Agency via Getty Images)  Heating and cooling of rocks repeatedly result in the expansion and contraction of the rock. When rock is exposed to high temperatures, it expands and as the temperatures cool, it contracts. This continual expansion and contraction cause the rocks to weaken and eventually break into pieces. Thermal expansion weathering is like Freeze-Thaw weathering. This Photo by Unknown Author is licensed under CC BY Abrasion is the grinding of rock by impact and friction during transportation. High-speed winds which carry pieces of sand have the capacity to break the rock when they sandblast on the surface of the rock. Abrasion makes rocks with sharp or jagged edges round-shaped and smooth. Wind abrasion - sandblasting effect on stationary rocks as seen in Arches National Park Moving water causes abrasion as particles in the water collide and bump against one another. Abrasion makes rocks with sharp or jagged edges round-shaped and smooth. Water abrasion- water & sediments flowing over boulders Notice the rounded river rocks Wind and Water Abrasion When a rock collides with one another, grinding of rock fragments takes place, and the rock is broken into pieces. ABRASION cuts them into smaller particles. Gravity causes abrasion when the rocks tumble down a mountainside and hit another rock, and break into fragments. It is the process by which saline solutions enter the cracks in a rock and evaporate, leaving behind salt crystals. When the temperatures rise, the accumulated salt crystals get heated and start to expand and release pressure on the rock, causing it to break. https://image2.slideserve.com/3755606/mechanics-of-salt-weathering-l.jpg  Plant Wedging It is caused by rainwater reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic. –The breakdown or decomposition of rock that occurs when minerals are changed into different substances –(change in composition) Involves water ,water vapor, Acids, and/or Oxygen O2  Solution Hydrolysis Oxidation  change in the composition of minerals when they react with water It is the breakdown of rock by acidic water to produce clay and soluble salts.  In hydrolysis, the chemical bonds of a mineral are broken down by water, creating a decomposition reaction. The bonds of H+ and OH- react together in water along with the minerals in the compound. The H+ ions are what react with the minerals to produce a weak acid. hydro- means water lysis means decomposition.  Feldspar Hydrolysis http://www.mii.org/Minerals/Minpics1/Plagioclase%20feldspar.jpg http://www.uwm.edu/Course/422-100/Mineral_Rocks/kaolinite1.jpg Feldspar Kaolinite (clay) Spheroidal weathering by hydrolysis, Holy Island, Anglesey. Spheroidal weathering by hydrolysis, Holy Island, Anglesey. Church carving showing effects of hydrolysis.  the process by which a mineral completely dissolves in water rocks that contain either magnesium carbonate or calcium carbonate, two substances which are easily dissolved by water or other acidic solutions  Carbon dioxide in the air dissolves in rainwater and becomes weakly acidic. This weak “carbonic acid” is able to dissolve limestone as it seeps into cracks and cavities. Over many years, solution of the rock can form spectacular cave systems, Ohio Caverns, shows the results of large-scale dissolution as water flowed through subsurface limestone. http://www.panoramio.com/photo/22535678  Chemical Weathering 1. Carbonation Carbonic Acid in water dissolves Calcite. This chemical weathering can hollow out underground Caverns Limestone and Dolomite both dissolve because they contain Calcite  Polluting gases, like sulphur dioxide and nitrogen oxide dissolve in rainwater to make stronger acids. When this rainwater falls, we get acid rain. This acid attacks many rock types, both by solution and hydrolysis, seriously damaging buildings and monuments. Acid rain (carbonic acid) weathering the details of statues and tombstones Ex: Marble and Limestone Damage to stonework caused by acid rain at Ephesus, Turkey Rainwater falling on this rock, and flowing along fractures in the rock, has slowly dissolved some of the limestone to create pits and channels. http://www.earth.ox.ac.uk/~oesis/field/medium/pavement1_1647.jpg  It is the breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty-colored weathered surface. Example: When oxygen reacts with metal elements in rock or on other surfaces creating oxides  Oxidation of minerals with iron (magnetite, pyrite) results in the formation of rust or iron oxide. this is why Mars is a red planet Copper turns rocks green  Pyrite Oxidation http://www.windows.ucar.edu/earth/geology/images/pyrite_sm.jpg Pyrite http://www.dkimages.com/discover/previews/965/75014124.JPG Limonite  MECHANICAL CHEMICAL PROCESS Physical Chemical disintegration disintegration thru chemical reaction PHYSICAL APPEARANCE YES YES CHEMICAL COMPOSITION NO YES TYPES Freeze-thaw weathering or Dissolution Frost Wedging Oxidation Exfoliation weathering or Hydrolysis Unloading Thermal Expansion Abrasion and Impact Salt weathering or Haloclasty Even Rocks Break! “What are the factors that could impact the rate at which rocks break?”  What is weathering? Describe the two types of weathering. References: https://uag-earthsci.blogspot.com/2019/11/day-048-giftionary-physical- weathering.html https://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3564.html