General Characteristics of the Earth

Internal Structure Crust: solid outer layer. Between 5-10 km beneath the oceans and 30-65km beneath the continents Mantle: The upper mantle is semi fluid and believed to cause continental drift. The lower mantle is solid despite high temperatures due to high pressure Core: Outer core is liquid (magnetic field), inner core is solid due to high pressure

Scientific understanding of Earth's internal structure is based on observations of topography, observations of rock in outcrop, samples brought to the surface from greater depths by volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of the gravity field of the Earth, and experiments with crystalline solids at pressures and temperatures characteristic of the Earth's deep interior.

Atmosphere This is an envelope of gas that surrounds the Earth It is a HOMOGENEOUS mixture (solution) of nitrogen (78%), oxygen (21%), water vapour (0.3%), carbon dioxide (0.03%), ozone (0.000 003%) and other trace gases

Layers of the Atmosphere

Troposphere: thicker near equator than at the poles Troposphere: thicker near equator than at the poles. Contains 80% of all the air in the atmosphere, produces weather phenomena, determines climate. Temperature DROPS with altitude Stratosphere: contains the ozone (O3) layer, which absorbs most ultraviolet rays. Airplanes usually fly here since there is less friction (less fuel)

Mesosphere: air molecules are scarce, but this layer can still protect us from meteoroids. Friction cause them to break apart Thermosphere: Thickest layer. Sun’s rays create extremely high temperatures. Ionosphere is found here, which can bounce radio waves due to the electrically charged particles it contains. Polar auroras happen in this layer. Meteoroids burn up here, too.

Human activities & the Atmosphere Chlorofluorocarbons (CFCs) and aerosol products caused thinning of ozone layer by reacting with it and transforming it into regular oxygen. Less protection from UV rays results in increased skin cancer, cataracts Ozone increased in the troposphere due to pollution irritates the mucous membrane of respiratory system

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Hydrosphere Formed by all bodies if water on Earth Fresh water make sup only 3% of Earth’s surface (glaciers, underground water, lakes & rivers) Most of this fresh water is frozen (ice caps, glaciers) so it’s inaccessible Four countries alone (Brazil, Canada,China & USA) possess nearly half the world’s fresh water

Lithosphere This comprises the Earth’s crust and part of the upper mantle Includes mountains, plains, volcanoes Contains minerals for plant growth, habitats for animals, has natural resources like oil & natural gas The lithosphere is constantly changing due to climate, human activity, etc..

Rock vs Mineral A rock is a HETEROGENEOUS mixture of different minerals in the form of grains A mineral is a pure substance. It is an inorganic (non-living) COMPOUND. (quartz, mica, feldspar). Minerals are classified according to color, hardness & magnetism

Rock formation Igneous rock is formed when magma cools & solidifies. It has crystals in it. (Granite) Sedimentary rock is formed when rock fragments are ERODED, transported and the deposited and compacted in layers (Limestone) Metamorphic rock is formed when rock undergoes a transformation due to heat and pressure. They have light and dark bands (gneiss) or sheets (slate)

Types of Soil Made up of matter which is a mixture of components from the lithosphere, hydrosphere and atmosphere Without it, life on Earth as we know it would be impossible It is formed when intact rock, called bedrock, is altered through erosion and mixed with organic material from living things

Erosion happens due to expansion of ice in rock fissures, which causes rocks to break. Acids in water also disintegrate rocks Organic matter accumulates due to debris from leaves, fruits, feathers, hair, excrement, carcasses. This forms humus in soil. Microorganisms also mix in to form soil.

Types of soil Soil is a mixture of sand, silt (fine particles smaller than sand) and clay (particles smaller than silt) Sandy loam is the most fertile soils. They are made up of one-third each sand, silt and clay.

Relief The Earth’s relief is constantly changing due to Pressure beneath Earth’s surface Winds Water & glaciers Human activity (roads, cities, towns)

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