Cultural Beliefs

From Genco

Contents 1 Earth Quakes 1.1 Earth means many things to people who live on it. 1.2 The surface of the earth. 1.2.1 The Crust 1.2.2 Mantle 1.3 Core

[edit] Earth Quakes

Ancient people invented many tales to explain their cause and source of these errors. Here are some of the ancient views that emerged:

• (Japan) The earth is carried on the back of a (spider). When the (spider) is angry, it shakes and causes the whole earth to tremble. Later the beast of burden became the (catfish) or (namazu). The (catfish) was prone to pranks and was watched by the god (Kashima). It was believed that whenever (his) attention was diverted the (catfish) would trash at his will an cause great earthquakes.In (October 1855), during the month without gods, a great quake strucked at (Edo (Tokyo)) thereby convincing many people regarding this ancient view.

• Many ancient people believed that the earth was held up by a great animal of some kind such as ox,dog,mole etc.

• The ancient Babylonians believed that quakes were caused by the wandering stars of Jupiter, Saturn and Mars. Basically the logic behind this view was that the additional gravity of the aligned planets caused earthquakes.

• Most people during the dark ages and beyond attributed the earthquake phenomenon to the anger of the God. For eg., five small quakes struck England in that year which caused no real damage but terrorized the English people. Thus at each successive quake more and more people were convinced of God's anger.

• Another belief that was came up at those times was that of the Hawaiian legends. It explained that eruptions were caused by Pele, the beatiful but temptuous Goddess of Volcanoes, during her frequent moments of anger. It was believed that she could cause earthquakes by stamping her feet and volcanic eruptions and fiery devastation by digging with the her magic stick.

• Finally came the ancient Greeks. The ancient Greeks were the first to attribute earthquake to scientific causes. They correctly noticed that the tsunamis followed many quakes, and concluded that the earthquake in the sea caused them.

Thus, we can see that many cultural beliefs came out but finally the Theory of Platetectnics was the apprropiate theory that explained the cause of earthquakes.

[edit] Earth means many things to people who live on it.

• To a farmer, earth is rich soil.
• To a road builder, erath means mountains of hard rock.
• To a sailor, earth is water.
• To a pilot, erath includes part of an ocean, a mountain, and patches of farmland.
• To an astronaut it is the earth's round shape, the outlines of land and oceans, and the clouds that cover them.

[edit] The surface of the earth.

[edit] The Crust

• The Hydrosphere
  • The hydrosphere is a layer of water, in the form of oceans, that covers approximately 70.8 percent of the surface of the earth.
• The lithos phere
  • The lithosphere consists of mainsly cold, ridig, rocky crust of the earth that extends to depths of 60 mi. (100 km)

[edit] Mantle

Mantle is furthur divided into three as shown in the above picture:

• Upper Mantle
• Transition Zone
• Lower Mantle

• Mantle is that region of the interior of the earth that lies between the outer crust and the core.

• The mantle is the largest of these regions and comprises the bulk of the Earth's mass and volume.

• The mantle is chemically distinct from both the crust and the core. It is composed of the rock peridotite, which principally consists of the minerals olivine, pyroxene, and amphibole. The crust contains lighter materials and the core is composed of iron and nickel.

• The mantle is separated from the crust by a sharp boundary known as the Moho.The Moho lies at a depth of about 8 km (5 mi) under the oceans and an average depth of about 35 km (about 22 mi) under the continents, but it digs to as deep as 80 km (50 mi) under tall mountain ranges.

• It is separated from the core by another sharp boundary known as the Gutenberg discontinuity. The Gutenberg discontinuity lies at a depth of about 2900 km (about 1800 mi).

• Temperatures in the mantle are high, reaching about 3700� C (about 6700� F).

• Pressures inside the mantle are also high, reaching about 137 gigapascals (1.37 million atmospheres).

• The mantle is solid, and its density increases with depth.

• Slow-moving currents called convection currents within the mantle play a part in the movement of the crustal plates on the earth.

The relative size of the mantle can be understood by likening the earth in cross-section to a soft-boiled egg. The eggshell represents the thin, hard crust of the earth, which only comprises about one half of one percent of the mass of the earth. The white of the egg represents the soft mantle, which comprises about two-thirds of the mass and about five-sixths of the volume of the earth. The yolk represents the core of the earth.

[edit] Core

The mantle and core are the heavy interior of the earth, making up most of the earth's mass.The core is also divided into two layers:

• Outer Core
• Inner Core

We can see from the above picture that the mantle is separated from the crust by a layer known as Moho and from the core by a layer known as Gutenberg Discontinuity.

The study of the earth is called geology, and scientists who study the earth are geologists.

The core is composed of mostly iron and nickel which remains very hot, even after 4.5 billion years of cooling. The core is divided into two layers:

• A solid Inner Core
• A liquid Outer Core

The core has an outer shell about 2225 km (1380 mi) thick with an average density of 10 known as the Outer Core. This shell is probably rigid, and research show that its outer surface has depressions and peaks.

The inner core, which has a radius of about 1275 km (795 mi), is solid. Temperatures in the inner core may be as high as 6650�C (12,000�F), and the average density is estimated to be 13.

Scientists used waves generated by earthquakes to determine that the outer core of the earth is liquid. Earthquakes generate P-waves and S-waves within the earth. Shadows occur on the opposite side of the earth from the earthquake epicenter because the outer core reflects S-waves, and bends P-waves.

S-waves are reflected because they cannot travel through liquids, and they cast a larger shadow than the bent P-waves. Geologists and seismologists determined the size of the outer core by using the 154-degree arc of the S-wave shadow and measurements taken on the surface of the earth.

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Earth's Crust consists of continents and ocean basins (lands beneath the oceans) which surrounds the main body of the earth. The thickness of the crust varies from about 8 kilometres under the oceans to about 40 kilometres under the continents.

The crust is made up of three kinds of rock:

• Igneous Rock

Igneous Rocks are formed when molten rock deep inside the crust cools and hardens or erupts at the surface as lava.igneous rocks are formed from molten material.

The two most common types of igneous rocks are Granite and Basalt. Granite is light colored and is composed of large crystals of the minerals quartz, feldspar, and mica. Basalt is dark and contains minute crystals of the minerals olivine, pyroxene, and feldspar.

• Sedimentary Rock

Sedimentary Rocks develop from materials that once were part of older rocks or of plants or animals. These materials were worn away from the land.

They then collected in low places, layer upon layer, and hardened into rock. Many sedimentary rocks contain shells, bones, and other remains of living things. Such remains, or the impressions of remains in sedimentary rocks, are called fossils.

• Metamorphic Rock

Metamorphic Rocks are formed deep in the crust when Igneous and Sedimentary rocks are changed by heat and the weight of the crust pressing on them.

Among the known metamorphic rocks, Quartzite and Marble are the most common. Quartzite is typically a tough, hard, light-colored rock in which all the sand grains of a sandstone or siltstone have been recrystallized into a fabric of interlocking quartz grains. Marble is a softer, more brittle, varicolored rock in which the dolomite or calcite of the parent sedimentary material has been entirely recrystallized.

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Types Of Crust

The crust is divided in two:

• The Sialic or Continental Crust or upper crust

It consists of continents and is made up of igneous and sedimentary rocks whose average chemical composition is similar to that of granite and whose density is about 2.7.

• The Simatic or Oceanic Crust or lower crust

It forms the floors of the ocean basins and is made of darker, heavier igneous rocks such as gabbro and basalt, with an average density of about 3.

All rocks on the earth's surface are made of minerals, the most common solid materials found on the earth. Minerals are themselves made up of basic chemical substances called elements. Rocks in the earth's crust consist mostly of two elements:

• Silicon
• Oxygen.

The most common elements in the earth's crust are:

• Aluminium
• Iron
• Calcium
• Sodium
• Magnesium

The bottom of the earth's entire crust is called the Mohorovicic discontinuity or Moho. It marks the boundary between the crust and the inner parts of the earth.