Friday, 28 October 2016

PLANET EARTH

Up to two thirds of the earth's rocky surface is covered by water.It is covered by a mixture of gases called atmosphere reaching 700 kilometers from earth's surface.

  • Earth spins around it's poles
  • The spinning earth acts like a magnet.
  • The different parts of the earth are - the thin rocky crust- the solid middle mantle- a central core.Outer part of core is liquid.Inner core solid metal.
  • The inner core is made mainly of iron and nickel.The temperature at the core is 6000 degree Celsius, hot enough to melt metals.The core is 2500 kilometers wide.
  • Around the centre flows a hot liquid layer of iron and nickel.This is the outer core,2200 metre thick.
  • As the earth spins the metal ball and liquid layer move at different speeds.Due to extreme pressure in the intensely hot inner core is solid.
  • The largest part of eartth's layer is called mantle which is 2900 kms thick. It is made of slow moving  rock.
  • Rocks in the upper mantle is comparable to the paste oozing out of the tooth paste tube when you squeeze it.
  • Earth's surface is covered by crust.
  • Land is made up of continental crust which is 20 kilometers to 70 kilometers thick.
  • Most of the crust is made of granite.
  • Ocean bed is made up of 8 kilometer thick oceanic crust.It is mainly made of a rock called basalt.
  • The crust is divided into huge slabs of rock called plates.Most plates have land and seas on top of them.
  • Pacific plate is mostly covered by water.
  • Areas of land on the plates are called continents. 
  • Africa,Asia,Europe,North America,South America,Oceania,and Antarctica are the 7 continents.
  • Very,very slowly ,the continents are moving.
  • As plates move so do the continents.In some places plates push into each other.
  • The continents are moving very very slowly.As plates move so do the continents.
  • In some places plates push into each other.At times they move apart.North America is moving 3 cms away from Europe every year.
  • There are places on earth, where hot,liquid rocks shootup through it's  surface.There are volcanoes.The huge space beneath a volcano filled with molten rock is  called Magma chamber.
  • As pressure builds up inside the chamber ash,steam,and molten rock(lava) erupts to the surface.
  • Volcanoes erupt in different ways and have different shapes.Volcanoes like those in Hawai have running lava.Others have thick lava.
  • There are volcanoes under the sea.The hot lava cooled quickly by the sea forms pillow shaped lumps called pillow lava.
  • The hot rocks don't always reach the surface.Huge lumps become struck.These are called batholiths.
  • Rocks cool slowly forming large crystals called granite.
  • A geyser can be found on the top of some old volcanoes.If these volcanoes collapse the gaps between the broken rocks make a group of pipes and chambers.Rain water seeps in ,collecting in the chamber where it is heated untill it boils.
  • Steam builds up, pushing the water through the pipes and out of a cone shaped opening called nozzle.Steam and water shoot through the nozzle, making a fountain up to 60 meters high.
  • There are springs in the ocean.They are called black smokers.
  • They form near rift volcanoes.Here water is heated by volcanoes' magma chambers.The hot water dissolves chemicals in the rocks, which turn black when they are cooled by surrounding clean water.They rise like clouds of smoke from chimneys.
GEYSERS
Geysers are common in the volcanic regions of New Zealand in Oceania.In some areas they are even used to help make electricity.
In a hot spring, the water bubbles gently into the surface.
Wallowing in a mud spot can make your skin soft and smooth.Mud pot is made when fumes break down rocks into tiny pieces.These mix with water to form mud making it bubble .Some mud pots are cool enough to wallow in.
rocks being broken down by ice 
Ice has the power to make rocks crumble.In cold weather rainwater gets into cracks in rocks and freezes.Water swells as it turns into ice.The ice pushes with such power that the rock opens up the rock.Over a long time a rock can be broken down to thousands of tiny pieces.
Living things can break down rocks.Seeds landed on rocks grows and it"s roots smash open the rock.Tiny living things called lichens dissolve the surface of rocks to reach minerals they need to live.Rabbits make burrows which break up some of the rock in the ground.
Warming up and cooling down can break rocks into flakes.

  • when a rock warms up it swells a little.when it cools the rock shrink back to it"s original size.
  • repeated swelling and shrinking cause some rocks to break up into flakes.Sometimes layers of flakes form on a rock and make it look like onion skin.
  • Glaciers break up rocks and carry them away.They slide away down mountainside and melt.As glacier moves,some rocks are snapped off and carried along.
  • Rocks in rivers and seas are always getting smaller.As the water flows it gradually wears the rock down.Water also dissolves minerals from the rock.Sand and grit slowly grind away the rock surfaces.
FOREST FACTS 
The speed at which forests are being cut down worldwide is slowing down from 8.3 million hectares  a year in 1990 - 2000 to 5.2 million in the past decade(2001- 2010).

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