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11.2B Folds, Faults, and Mountains Mountains, Plateaus, Domes and Basins.

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Presentation on theme: "11.2B Folds, Faults, and Mountains Mountains, Plateaus, Domes and Basins."— Presentation transcript:

1 11.2B Folds, Faults, and Mountains Mountains, Plateaus, Domes and Basins

2 T ypes of Mountains  Folding and faulting produce many but not all of Earth’s mountains.  In general, mountains are classified by the processes that formed them  T he major types of mountain types include Volcanic mountains Folded mountains Fault-block mountains Dome mountains

3 M ountain Ranges T ypes of Mountains :  Geologists refer to the collection of processes involved in mountain building as orogenesis. The term is derived from the Greek oros meaning “mountain” and the –geny meaning “born”.  Earth’s mountains do not occur at random. Several mountains of similar shape, age, size and structure form a group called a mountain range.

4 M ountain Systems T ypes of Mountains :  A group of different mountain ranges in the same region form a mountain system.  The Sangre de Cristo and West Elk mountain ranges form part of the Rocky Mountain system. Sangre de Cristo Mountains Range Rocky Mountain System

5 V olcanic Mountains  Recall from the previous chapters that volcanic mountains form along plate boundaries and at hot spots.  In addition, igneous activity forms rock deep in the crust that can be uplifted as a result of plate motions and isostatic adjustment.

6 F olded Mountains  M ountains that are formed primarily by folding are called folded mountains.  Compressional stress is the major cause of folded mountains.  Compressional stress helped to form the Alps in Europe.  Thrust faulting is also important in the formation of folded mountains, which are often called fold-and- thrust belts.

7 F olded Mountains  F olded mountains often contain numerous stacked thrust faults that have displaced the folded rocks layers many kilometers horizontally.  The Appalachian Mountains, the northern Rocky Mountains, and the Alps in Europe are all examples of folded mountain ranges. Stacked thrust faults

8 F ault-Block Mountains  Fault block mountains; another type of mountain formation, is the result of movement along normal faults.  Most normal faults are small and have displacements of only a meter or so.  Others extend for tens of kilometers where they may outline the boundary of a mountain front. Examples fault block mountains

9 F ault-Block Mountains  Large scale normal faults are associated with fault-block mountains  Fault-block mountains form as large blocks of crust are uplifted and tilted along normal faults. Examples fault block mountains

10 G rabens and Horsts  Normal faulting occurs where tensional stresses cause the crust to be stretched or extended.  As the crust is stretched, a block called a graben, which is bounded by normal faults, drops down.  Grabens produce an elongated valley bordered by relatively uplifted structures called horsts.

11 G rabens and Horsts  The Basin and Range regions of Nevada, Utah, and California is made of elongated grabens.  Above the grabens, tilted fault- blocks or horsts produce parallel rows of fault-block mountains. Sierra Nevada Range

12 G rabens and Horsts  In the western US, other examples of fault block mountains include the Grand Tetons and the Sierra Nevada Range in California.  These steep mountain fronts were produced over 5 to 10 million years by many episodes of faulting. Sierra Nevada Range

13 P lateaus, domes, basins  M ountains are not the only landforms that result from forces in Earth’s crust.  Up and down movements of the crust can produce a variety of landforms, including plateaus domes basins.

14 P lateaus  A plateau is a landform with a relatively high elevation and more or less level surface.  To form a plateau, a broad area of the crust is uplifted vertically; raised above the adjoining landscape.  Plateaus can cover very large areas of land such as the Colorado Plateau which stretches over four states. Colorado Plateau

15 D omes  Broad upwarping in the rock underlying an area may deform sedimentary layers.  When upwarping produces a roughly circular structure, the feature is called a dome.  Domes often have the shape of an elongated oval.  You can think of the upwarped layers that make up a dome as a large fold.

16 B asins  Downwarped structures that have a roughly circular shape are called basins.  The central United States contains a number of basins, including the large Michigan Basin. Michigan Basin

17 B asins  During mountain building, plate motions can cause the crust to bend downward and form a basin.  If the basin sinks below sea level, it may form a shallow sea.  Over time, sediments such as sand and the skeletons of ocean creatures are laid down, forming layers of sedimentary rock. Michigan Basin

18 B asins  Basins may also form along the edges of continents where thick layers of sediment build up. The weight of the sediment downwarps the crust to form a basin.  When forces in the crust uplift the sedimentary layers, the rock that fills the basin is exposed at the surface. Michigan Basin

19 B asins  Look at the map of the Michigan Basin to the right; it resembles a bull’s eye. The oldest rocks are around the edges of the basin and the youngest rocks are near the center. Michigan Basin

20 B asins  The plate motions that help to form sedimentary basins can also destroy them.  For example, when two continental plates collide, the ocean basin between them closes up.  Sedimentary rock in the basin becomes part of the landmass formed by the collision. Michigan Basin

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