Post on 02-Dec-2014
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DESCRIPTIONA short description of beach formations and how they most commonly are formed. For elementary science students.
- 1. How BeachesAre Formed?By Moira Whitehouse PhD
2. Before exploring how beaches areformed lets talk about the main typesof beaches.There are two main types of beaches1. Rocky beaches2. Sandy beaches 3. Rocky Beaches (most with cliffs) Are often made of volcanic rock. Include four kinds of landforms: seacliffs, sea arches, sea stacks and seacaves. 4. Sea Cliffs 5. Sea Caves 6. Sea Arches 7. Sea Stacks 8. Rocky beaches are shaped by weathering,erosion and deposition caused by waves(water) and wind.The constant beating of the cliffs and seastacks weather and erode the rock.Eroded material is then depositedbecoming available to form sand bars andbarrier islands. 9. Because of the severe pounding ofboth wind and waves, theseformations erode relatively quickly.Over a long period of time sea stacksometimes completely weather and erodeaway.The following series of pictures shows thesame sea stack photographed over a 100year period. 10. 1890 http://walrus.wr.usgs.gov/pubinfo/jump.html1910 11. http://walrus.wr.usgs.gov/pubinfo/jump.html19101920 12. 19701990 13. Sea arches and seacaves are createdwhen part of the rockmaking up a cliff isharder than otherparts. The softersection can not standthe erosive powers ofthe waves for as longas the harder sectionand erodes faster. 14. The softer material in this span has alreadyeroded, leaving the harder rock spanning the arch.http://www.flickr.commikebairdThe softer rock in this cliff hasalready eroded, leaving a sea cave. 15. Sandy Beaches Are deposition landforms, meaningthat they are formed by deposits ofsediment.The sediments deposited are sand, silt andpebbles materials carried by a river orstream from the inland into the ocean;River sediments are the source of most ofthe sand on beaches. 16. Washed to sea by streams and rivers, twoseparate processes result in the deposit ofthis sand and sediment on the shore. Some of the sediment is depositedimmediately at the mouth of the river oftenforming a delta. Most of the sediment becomes suspendedin sea water and is carried along the coast bythe longshore current, a stream of waterflowing parallel to the beach. This current iscreated by waves breaking at an angle toshore. 17. Sandy beaches can be a lot of fun....but this drivershould have known something about tides beforetaking the car on the beach. 18. Rocks and sediment deposited at the footof a glacier where the glacier melts createa landform called a moraine. THE END