Glacial sedimentation is very diverse, and generally consists of the most poorly-sorted sediment deposits found in nature. The main clast type is called diamictite , which literally means two sizes, referring to the unsorted mix of large and small rock fragments found in glacial deposits.
Many glacial till General term for very poorly sorted sediment that is of glacial origin. The surfaces of larger clasts typically have striations from the rubbing, scraping, and polishing of surfaces by abrasion during the movement of glacial ice. In addition to mineral composition and lithification process, geologists also classify sedimentary rock by its depositional characteristics, collectively called facies or lithofacies.
Geologists analyze sedimentary rock facies to interpret the original deposition environment, as well as disruptive geological events that may have occurred after the rock layers were established. It boggles the imagination to think of all the sedimentary deposition environments working next to each other, at the same time, in any particular region on Earth.
The resulting sediment bed A specific layer of rock with identifiable properties. For example in the Grand Canyon, rock strata of the same geologic age includes many different depositional environments : beach sand, tidal flat silt, offshore mud, and farther offshore limestone. In other words, each sedimentary or stratigraphic facies presents recognizable characteristics that reflect specific, and different, depositional environments that were present at the same time.
Facies may also reflect depositional changes in the same location over time. During periods of rising sea level, called marine transgression , the shoreline moves inland as seawater covers what was originally dry land and creates new offshore depositional environments. When these sediment bed A specific layer of rock with identifiable properties.
Biological facies are remnants coal Former swamp-derived plant material that is part of the rock record. The horizontal assemblage and vertical distribution of fossils are particularly useful for studying species evolution because transgression , deposition , burial, and compaction processes happen over a considerable geologic time range.
During the Middle Cambrian period see Chapter 7, Geologic Time , regions around the Grand Canyon experienced marine transgression in a southeasterly direction relative to current maps. This shift of the shoreline is reflected in the Tapeats Sandstone beach facies , Bright Angle Shale near- offshore mud facies , and Muav Limestone far- offshore facies.
Marine organisms had plenty of time to evolve and adapt to their slowly changing environment; these changes are reflected in the biological facies , which show older life forms in the western regions of the canyon and younger life forms in the east. Which of the following depositional environments is least likely to form fine-grained mud?
Glacial environments typically produce sediments with a wide range of grain sizes. Which of the following depositional environments has the least water? Aeolian is transport and deposition by wind, without water involved. A stratum with a mix of sandstone and conglomerate sedimentary rocks with ripple marks, cross bed A specific layer of rock with identifiable properties. Facies ties the classification of sedimentary rocks to the environment in which they formed.
Which of these is the typical facies distribution along a shoreline? The typical facies distribution along a shoreline is sand on the beach, mud along the nearshore , and limes forming in the far offshore. On the dynamic Earth, shifting environments over time cause facies distributions that allow interpretation of ancient shifting shorelines. In the Middle Cambrian strata of the Grand Canyon and surrounding regions, facies interpretation shows that, relative to modern directions, the ancient Cambrian ocean transgressed how?
Study of facies in the Cambrian Tapeats Sandstone , Bright Angel Shale , and Muav Limestone and equivalent rock strata in the region show a transgression of the Middle Cambrian ocean from northwest to southeast across the region during that ancient time. Which of the following depositional environments is most likely to be at the lowest elevation? Paludal swamp deposition is commonly coastal or in other low elevation locations.
Sedimentary rocks are grouped into two main categories: clastic detrital and chemical. Clastic detrital rocks are made of mineral clasts or sediment that lithifies into solid material. Sediment is produced by the mechanical or chemical weathering of bedrock and transported away from the source via erosion.
Sediment that is deposited, buried, compacted, and sometimes cemented becomes clastic rock. Clastic rocks are classified by grain size ; for example sandstone is made of sand-sized particles. Chemical sedimentary rocks comes from minerals precipitated out an aqueous solution and is classified according to mineral composition.
The chemical sedimentary rock limestone is made of calcium carbonate. Sedimentary structures have textures and shapes that give insight on depositional histories. Depositional environments depend mainly on fluid transport systems and encompass a wide variety of underwater and above ground conditions. Geologists analyze depositional conditions, sedimentary structures, and rock records to interpret the paleogeographic history of a region.
Use this quiz to check your comprehension of this chapter. Which property of water is most involved in chemical weathering? Because water is a universal solvent , it can chemically break down any rock, given enough time. Which is the correct order of grain sizes from smallest to largest for clastic detrital sedimentary rocks?
Clay is the smallest, boulder is largest. What mainly causes agents of transport, like wind or water, to deposit sediment? Typically, a slower speed of flow causes material to deposit. When the speed of flow of the medium drops below the settling velocity of a particle, it will settle out.
What story does a sedimentary rock tell you? Study of sedimentary rocks and depositional environments can reconstruct past landscapes. Which of the following is NOT part of the process of diagenesis and lithification of sediment into sedimentary rock? Melting belongs in another part of the rock cycle. What makes a shale different than a mudstone? Shale is fissile , meaning it has many thin layers. While there may be some detailed differences in environmental factors, the fundamental difference is layering.
Imagine a new and previously unknown sedimentary structure is discovered in a deposit of sedimentary rock. What would be the best approach to try and understand it? Sedimentary structures are compared to their modern counterparts e. Soils make which essential element accessible to life? Nitrogen is an essential element for life, but is mainly found and supplied to life via soil A type of non-eroded sediment mixed with organic matter, used by plants.
What is the most important thing that all sedimentary rocks can tell you, specifically regarding depositional environment? Study of sedimentary rocks including the environments in which they formed provides information about the ancient geography and landscapes on the Earth at that time.
What do chemical and detrital sedimentary rocks have in common? Think about it. Wind may have been the transporting medium for some detrital sediments , but water was involved in the weathering and lithification of all sedimentary materials.
Good thinking. The House Range contains early Paleozoic marine rocks, highlighted by the Wheeler Formation, home to some of the best Cambrian fossils in Utah. Notch Peak contains one of the largest pure-vertical drops in North America at over feet. The water molecule consists of two hydrogen atoms covalently bond. Found more toward the equator. Positive and negative side. Dissolves better than normal water. Found more toward the poles.
More pure than normal water. What property of water causes it to form droplets as it rains? Specific gravity. Hydrogen bonds. Specific heat. A type of non-eroded sediment mixed with organic matter, used by plants.
Valuable material in the Earth, typically used for metallic mineral resources. Weathering describes the physical removal of sediments from one place to another, while erosion is the physical breakdown that forms those sediments. Weathering describes the physical removal of sediments from one place to another, while erosion is the chemical breakdown that forms those sediments.
Weathering describes how rocks breakdown into smaller pieces, while erosion is the physical removal of those pieces to another location. Weathering is when oxygen attacks the rock, while erosion is when water freezes in the cracks causing the rocks to break apart into smaller pieces. Weathering describes how weather such as rain and temperature affects the rocks, while erosion is the physical deposition of sediment into a river. Which of these is NOT a component of soil.
Organic material humus. Weathered rock. Eroded rock. Oxidation rusting , dissolution , hydrolysis , and formation of soil. Mechanical weathering adds strength to chemical weathering. Mechanical weathering creates surfaces for chemical weathering to take place. Chemical weathering adds speed to mechanical weathering. Chemical weathering creates surfaces for mechanical weathering to take place.
Chemical weathering adds strength to mechanical weathering. Empty space in a geologic material, either within sediments, or within rocks. An atom or molecule that has a charge positive or negative due to the loss or gain of electrons.
Porous variety of carbonate that form in relatively unheated water, sometimes as towers and spires. Spheres of calcite that form in saline waters with slight wave agitation. A topographic high found away from the beach in deeper water, but still on the continental shelf. Banded iron formation. Fossiliferous sandstone. Shale and sandstone are detrital even if they include fossils , banded iron formation is chemical, and coal.
Longer distance transported. Shorter time since weathering. Higher temperatures in environment. Lack of water in environment. Stronger bedrock. A large pile of sediment, deposited perpendicular to flow. Material filling in a cavity left by a organism that has dissolved away. Graded bedding. Asymmetrical ripple marks. Symmetrical ripple marks. Fissile shale. Which of these indicate changing water conditions, from wet to dry? Ripple marks. Raindrop impressions. Geopetal structures. Sole marks.
Which of these forms from a slower speed of flow? Chutes and pools. Upper plane bed. Next fastest are cross bed. Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course.
A rock layer that has been bent in a ductile way instead of breaking as with faulting. Movements of water rising and falling due to the gravity of the moon and sun.
A stratum with a mix of sandstone and conglomerate sedimentary rocks with ripple marks, cross bed. Upper shoreface. Lower shoreface. Offshore limes , Beach sand , Nearshore mud. Paludal organic deposits , Nearshore mud , Offshore limes. Nearshore mud , Beach sand , Offshore limes. Beach sand , Nearshore mud , Offshore limes. Beach sand , Paludal organic deposits , Nearshore mud.
East to west. Northwest to southeast. Southeast to northwest. North to south. Chapter 5 Review Use this quiz to check your comprehension of this chapter. High boiling point. Universal solvent. Less dense when solid. Decreased weathering. Increased carbon dioxide.
Increased weathering. Decreased transport speed. Decreased temperature. Number of organisms present. Types of volcanoes present. Ideas about ancient landscapes. Volume of the river that made them. Ideas about temperature in the past. Depositional environment. Darker colored. Thinly bedded fissile. Different minerals. Look at the rocks above and below it.
Find a similar structure in a modern environment. Examine the thickness of the layer. Look for microfossils within the layer. Examine the minerals found within the layer. Nitrogen is an essential element for life, but is mainly found and supplied to life via soil. Speed of the river that made them. Types of organisms present. Both were made by erosion. Both involved water in their formation. Both come from older bedrock. Both made by organisms. Both have rounded grains. Affolter, M.
Ayrton, H. Bagnold, R. Flow Regime part. Plane bed. Lower plane bed , flat laminations. Small with respect to flow inclined layers dipping downflow. Larger inclined cross bed A specific layer of rock with identifiable properties. Flat layers, can include lined-up grains parting lineations. Hard to preserve reverse dune A large pile of sediment, deposited perpendicular to flow. Erosional, not really a bedform ; rarely found preserved.
Common Rock Types. Typical Fossils. Sedimentary Structures. Submarine fan. Continental slope. Littoral beach. Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity. Mechanical weathering physically breaks up rock. One example is called frost action or frost shattering. Water gets into cracks and joints in bedrock. When the water freezes it expands and the cracks are opened a little wider.
Figure 3. Rocks on a beach are worn down by abrasion as passing waves cause them to strike each other. Abrasion makes rocks with sharp or jagged edges smooth and round. If you have ever collected beach glass or cobbles from a stream, you have witnessed the work of abrasion figure 3.
Now that you know what mechanical weathering is, can you think of other ways it could happen? Plants and animals can do the work of mechanical weathering figure 4. Burrowing animals can also break apart rock as they dig for food or to make living spaces for themselves. Figure 4. Mechanical weathering increases the rate of chemical weathering. As rock breaks into smaller pieces, the surface area of the pieces increases figure 5.
With more surfaces exposed, there are more surfaces on which chemical weathering can occur. Figure 5. Mechanical weathering may increase the rate of chemical weathering. Chemical weathering is the other important type of weathering. Chemical weathering is different from mechanical weathering because the rock changes, not just in size of pieces, but in composition. That is, one type of mineral changes into a different mineral.
Chemical weathering works through chemical reactions that cause changes in the minerals. Most minerals form at high pressure or high temperatures deep in the crust, or sometimes in the mantle. This is a very different environment from the one in which they formed and the minerals are no longer stable. Many silicate minerals form in igneous or metamorphic rocks. The minerals that form at the highest temperatures and pressures are the least stable at the surface.
Clay is stable at the surface and chemical weathering converts many minerals to clay figure 6. There are many types of chemical weathering because there are many agents of chemical weathering. Water is the most important agent of chemical weathering.
Two other important agents of chemical weathering are carbon dioxide and oxygen. A water molecule has a very simple chemical formula, H 2 O, two hydrogen atoms bonded to one oxygen atom. But water is pretty remarkable in terms of all the things it can do.
The positive side of the molecule attracts negative ions and the negative side attracts positive ions. So water molecules separate the ions from their compounds and surround them. Water can completely dissolve some minerals, such as salt.
Follow this link to check out this animation of how water dissolves salt. Hydrolysis is the name of the chemical reaction between a chemical compound and water. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. The rock cycle is a web of processes that outlines how each of the three major rock types—igneous, metamorphic, and sedimentary—form and break down based on the different applications of heat and pressure over time.
For example, sedimentary rock shale becomes slate when heat and pressure are added. The more heat and pressure you add, the further the rock metamorphoses until it becomes gneiss. If it is heated further, the rock will melt completely and reform as an igneous rock.
Empower your students to learn about the rock cycle with this collection of resources. An element is a substance that cannot be broken down into a simpler format. They are distinguished by a unique atomic number. The elements are organized by their atomic number in the periodic table, which highlights elements with similar properties. Water is an example of a compound, a mixture of two or more elements, and is created when two hydrogen atoms bond to an oxygen atom.
Use these resources to examine the properties and uses of elements and compounds. Weathering is the process of the weakening and breakdown of rocks, metals, and manmade objects. There are two main types of weathering: chemical and physical. An example of chemical weathering is acid rain.
Caused mostly by the burning of fossil fuels, acid rain is a form of precipitation with high levels of sulfuric acid, which can cause erosion in the materials in which it comes in contact. An example of physical weathering is wind blowing across the desert playas.
This process causes rocks to form a specific pyramid-like shape and they are called ventifacts. Select from these resources to teach about the process of weathering in your classroom. Sedimentary rocks are one of three main types of rocks, along with igneous and metamorphic. Metamorphic rocks start as one type of rock and—with pressure, heat, and time—gradually change into a new type of rock. Join our community of educators and receive the latest information on National Geographic's resources for you and your students.
Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Weathering describes the breaking down or dissolving of rock s and mineral s on the surface of the Earth.
Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Together, these processes carved landmark s such as the Grand Canyon, in the U. This massive canyon is kilometers miles long, as much as 29 kilometers 18 miles wide, and 1, meters 1 mile deep.
Weathering and erosion constantly change the rocky landscape of Earth. Weathering wears away exposed surfaces over time. The length of exposure often contributes to how vulnerable a rock is to weathering.
Rocks, such as lava s, that are quickly buried beneath other rocks are less vulnerable to weathering and erosion than rocks that are exposed to agents such as wind and water. As it smoothes rough, sharp rock surfaces, weathering is often the first step in the production of soil s. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil.
Soils types associated with a mixture of weathered rock include glacial till , loess , and alluvial sediment s. Weathering is often divided into the processes of mechanical weathering and chemical weathering. Biological weathering , in which living or once-living organisms contribute to weathering, can be a part of both processes.
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