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Geography Questions: Our Latest Answers | |
<<Chemistry answers | Math answers | Geography answers>> 1. What do the layers of limestone in a rock outcrop indicate that the area had at some time been? Many animals and some water plants draw calcium carbonate out of the water and use it to make their shells and bones. The oysters, clams, snails, corals, and sea urchins do this. When the animals die, the shells and bones are broken up by waves into shell and coral sand and mud. Many of the beaches on Pacific islands are made of such coral mud and sand. Most of the limestone layers in all parts of the earth were once shell or coral sand and mud. 2. By what are the Igneous rocks formed by? Igneous rock is rock formed by the hardening and crystallization of molten material that originates deep within the earth. This material, called magma, is usually a mixture of liquid rock, gases, and mineral crystals. Igneous rocks are one of the three major types of rocks. The other types are metamorphic rocks and sedimentary rocks. 3.From what is the most common igneous rock in the ocean floor formed from? Two principal types of igneous rocks are basalt and granite. Basalt is an extrusive rock, and granite is an intrusive rock (Extrusive rocks form when magma flows onto the surface of the earth or floor of the ocean and then cools and hardens. Intrusive rocks result when magma cools until it solidifies beneath the earth's surface). Basalt consists chiefly of the silicate minerals plagioclase feldspar and pyroxene. Basalt occurs on volcanic islands and makes up a large part of the oceanic crust, including the mid-ocean ridges. 4.From what are the most violent volcanic explosions generally generated from? Also called Phreatic Eruption (Explosion): An explosive volcanic eruption caused when water and heated volcanic rocks interact to produce a violent expulsion of steam and pulverized rocks. Magma is not involved. 5. What is the majority of surface rocks? (clue: is it sedimentary, extrusive, intrusive, or metamorphic?)
Metamorphic as continents consist largely of granite and of metamorphic rocks that are formed from granite. 6. Of the following rocks, the one that does not originate in sediments laid down by water, wind, or ice is: (briefly explain why). (sandstone) (shale) (marble) (conglomerate) Marble: it is a metamorphic rock. Metamorphic rock is rock that has been changed by heat or by heat and pressure. This type of rock results from chemical and structural changes that occur in solid rock buried in the earth's crust. Metamorphic rock can be formed from the two other main kinds of rock, igneous and sedimentary. It also may be produced from other metamorphic rock. There are many types of sedimentary rock and they have a variety of uses. The most common sedimentary rock is shale. It is made of compressed mud--that is, a mixture of clay and silt (fine particles of mineral matter). Shale is used in making bricks. Limestone, another common sedimentary rock, is made chiefly of the mineral calcite. Limestone is used for building, making chalk, and various other purposes. Cement is made of limestone with a little shale mixed in. Sandstone, made of sand, and conglomerate, composed of sand or gravel particles, are also used for building. The sand or gravel particles in sandstone and conglomerate are held together by a mineral cement. Coal, consisting entirely of compressed plant remains, is a major source of fuel. 7.What are the rocks that are altered by heat and pressure beneath the Earth's surface? Metamorphic rock forms when any kind of rock undergoes changes as a result of intense heat and pressure. 8. What could compression not produce? (clue: reverse faults, normal faults, synclines, or anticlines?) briefly explain. Normal faults generally occur in places where the lithosphere is being stretched, so they cannot be formed by compression. Consequently they are the chief structural components of many sedimentary rift basins (e.g. the North Sea) where they have major significance for hydrocarbon exploration. They can also be found in deltas, at the rear edges of huge gravitation slumps and slides. 9. Where is the Earth's magnetic field generated in? It is generally accepted that the primary field is generated by electrical currents flowing in the molten metallic inner layer of the earth. 10. The propagation of seismic waves through the Earth's interior provides evidence of internal layering. The 1st boundary was the boundary between the _______________.
Crust and the mantle |
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