Earth's Solar System & Structure PDF

The Earth in Space You will be here. The Solar System that we live in consists of a medium-size star (the Sun) with eight planets orbiting it. The planets are of two different types; –The inner planets (Terrestrial Plants) Rocky planets near the Sun Mercury, Venus, Earth & Ma...

The Earth in Space You will be here. The Solar System that we live in consists of a medium-size star (the Sun) with eight planets orbiting it. The planets are of two different types; –The inner planets (Terrestrial Plants) Rocky planets near the Sun Mercury, Venus, Earth & Mars Arc, small, high density, rocky, poor in ices and H/He and no rings The outer planets (Jovian Planets).Giant gaseous planets.Jupiter, Saturn, Uranus, Neptune. Large, low density, gaseous (H, He, CH4), rotate rapidly.. All have rings and have many moons. Pluto, a small icy minor planet  Differences between inner and outer planets: – Density – The rocky inner planets=densities of 3 g/cm3 more – The gaseous outer Planets=densities of 1.6 g/cm3 or less ORIGIN OF THE EARTH AND THE SOLAR SYSTEM Fig. 1: Sketch of Nebular theory How old of the Earth? Age of the Earth 4.5 to 4.6 billion years (4,500,000,000 to 4,600,000,000 years) as determined through radiometric dating (Uranium, Thorium), using an instrument called a mass spectrometer. Where do we find the oldest rocks on Earth? Canadian Shield. (NW Territories near Great Slave Lake, 3.96 by). Before this, oldest rocks known were from Isukasia region of Greenland (3.8 by).  Spheres of the Earth There are Four spheres of the earth: atmosphere, hydrosphere, biosphere and lithosphere. Lithosphere: This crust is composed of igneous, sedimentary and metamorphic rocks. Hydrosphere: Total mass of water on or near the Earth’s surface -Covers 71% of Earth’s surface ~98% in oceans 2% in glaciers, groundwater, lakes and streams (fresh water) Biosphere: It includes all life on the earth either plant life or animal life, in the sea or onland.  Atmosphere: -78% nitrogen -21% oxygen Minor amounts of carbon dioxide, argon and water vapor It is divided into several layers arranged upwards from the earth's surface: Troposphere (where weather takes place), Stratosphere (where the ozone layer that protects the surface of the Earth from UV rays is found), Mesosphere, Thermosphere and Exosphere (which grades off into outer space)  Earth Structure How do we know what the Earth's Interior is like? 1.Drilling: -Wells drilled into Earth are mostly in the upper 7 km of the crust. Deepest well- Soviet (Russian) well in northern Kola Peninsula 20 year effort to drill a 12 km hole and stopped in 1989. Costs are more than $100 million, bottom hole temperature is 190°C Current status? 2-Volcanic activity: -Materials are brought up from below. Xenoliths = foreign rock (pieces of the mantle in lava) example: Only useful to depth of about 200 km. 3- Samples of the solar system (meteorites). 4- Study of seismic waves generated by earthquakes and nuclear explosions. Ordinary Chondritic Meteorite -composition of asteroids and the early solar system -pyroxene chondrule in thinsection -chondrules The Earth is divided into three chemical layers: the core, the mantle and the crust (Fig.). Fig.: The layers of the earth.  Earth’s Internal Structure Solid Earth has a layered structure – Layers defined by composition and physical properties –Compositional layers crust - mantle - core –Physical layers lithosphere - asthenosphere - mesosphere - outer core - inner core  Compositional Layers Crust –Outermost compositional layer –Definite change in composition at the base of the crust –2 types: Continental crust (Granite) Oceanic crust (basalts) Fig. Lithosphere and asthenosphere  Crust –Continental crust Thick - up to 75 km Lower density - 2.7 g/cm3 Strongly deformed Much older - may be billions of years old  Crust –Oceanic crust Thinner - about 8 km More dense - 3.0 g/cm3 Comparatively undeformed Much younger - < 200 million years old  The asthenosphere is part of the mantle that flows. It might seem strange that a solid material can flow.  Physical Layers Lithosphere – Crust + upper portion of the mantle – Solid & rigid – Thickness ranges from 10 km beneath oceans to 300 km in continental areas 2- Mantle is the middle layer of the Earth, is made of minerals rich in the elements iron, magnesium, silicon, and oxygen. Al over I000°C, the mantle is solid but can deform slowly in a plastic manner.. The core is composed of iron and nickel and remains very hot, even after 4.5 billion years of cooling. The core is divided into two layers: a solid inner core and a liquid outer core. The inner Core is under such extreme pressure that it remains solid. Exploring the Earth's Core How was the Earth's core discovered? Recordings of seismic waves from earthquakes gave the first clue. * P and S wave travel times depend on properties of rock materials that they pass through. Wave velocity depends on density and elasticity of rock. Seismic waves travel faster in denser rock. Speed of seismic- waves increases with depth as pressure and density increase downward.