earth structure

• planet


  sizeable object orbiting a star massive enough to have its own gravity

  elliptical and co-planar orbits in the same direction as the suns rotation
• comets


  made of ice and dust

  outer layer melts to water vapor close to the sun
• the sun


  a yellow dwarf star composed of hydrogen and helium 99.8% of total mass of solar system
• meteorites


  rocky fragments falling to earth from space
• asteroids


  rocky objects that failed to form a planet
• moons


  natural satellites that orbit planets
• mercury


  heavily cratered, signs of volcanism, iron rich core, thin atmosphere, no moons,
• Venus


  no oceans, craters, shield volcanos and lava flows, huge greenhouse effect, dense atmosphere, sulfuric acid clouds
• mars


  large shield volcanos, water in ice caps, sedimentary rocks and structures
• Jupiter


  small rocky metallic core, powerful magnetic field, H+He cloud, great red spot- huge storm, 63+ moons and volcanically active
• Saturn


  rings made of ice, rocky core, powerful storms, second largest moon in the solar system
• Uranus


  icy rings, orbits on the side, windy, 27 major moons, methane atmosphere
• neptune


  great dark spot, magnetic field, rocky core possible, 14 known moons.
• solar system


  8 planets

  four inner terrestrial planets

  four outer Jovian gas giants

  172 moons and natural satellites

  asteroid belt

  Kuiper belt
• asteroid belt


  the region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found
• Kuiper Belt


  A region of the solar system that is just beyond the orbit of Neptune and that contains small bodies made mostly of ice
• terrestrial


  internal structure similar

  differentiated

  topographic features on surface

  silicate rocks composition

  secondary atmosphere
• the moon


  lunar maria- dark and made of basalt- flat w few craters

  lunar highland- pale, anorthosite, steep topography, heavy craters

  collision- giant impact hypothesis
• Jovian Planets

  large and low density

  composed of gas (hydrogen, helium ,methane and ammonia)

  all have a planetary ring system

  mobile surface features

  all rotate rapidly causing strong east-west wind direction- leads to formations of bands or stripes
• Io- Jupiter moon


  massive volcanic plumes

  most volcanically active place in solar system

  gravity from other bodies causes it to change shape- friction

  heat and melting of rock caused
• birth of the solar system

  -Material that did not become a star in the nebula forms protoplanetary disk

  -Contains all 92 elements as solitary atoms or clumps

  -Planetesimals form (>1km)

  -Protoplanets form

  -Inner planets (terrestrial) form from dust

  -Outer planets (gas) form from ice and other gases
• Earth structure- compositional layers


  continental crust

  oceanic crust

  moho

  mantle

  Gutenberg discontinuity

  core
• Earth structure- mechanical layers

  lithosphere

  asthenosphere

  inner mantle

  outer core

  Lehmann discontinuity
• crust


  oceanic and continental
• continental crust


  made from granite

  rich in silicone and aluminum

  all rock types

  av density 2.7 g/cm3

  all ages up to 4Go

  average thickness 35km
• oceanic crust


  basalt, dolerite, gabbro

  mafic igneous rock

  rich in iron and magnesium

  av density 2.9 g/cm3

  up to 200ma

  average thickness 7km
• Moho


  the boundary between the earth's mantle and crust
• upper mantle


  solid silicate rocks

  main peridotite made of augite and olivine

  xenoliths may occur

  topmost upper mantle is cooler, rigid and responds in brittle manner

  together with crust is lithosphere

  rest of the upper mantle deforms in a ductile manner but is still solid
• the lower mantle


  solid- less ductile due to great pressure

  composition similar to stony meteorites

  convection currents from core-mantle boundary
• outer core


  boundary between the lower mantle and outer core is called the Gutenberg discontinuity

  liquid state

  Fe-Ni alloy similar in composition to iron meteorites

  extends from 2900-5150km

  convection currents also occur

  source of the earths magnetism
• inner core


  solid state

  Fe-Ni similar to iron meteorites

  extends from 5150-6371km - Centre of the earth
• mechanical layers


  crust and mantle are based on the compositions of the rocks

  lithosphere and asthenosphere are based on the properties of the rocks that mean they react in different ways due to temp and pressure
• the lithosphere


  composed of part of the crust and topmost mantle

  includes the moho which marks the base of the crust

  the base of lithosphere is marked by a change in physical properties rather than a change in composition

  base of lithosphere lies at the 1300 isotherm
• asthenosthere


  next layer underneath, forms next part of the upper mantle down to approx. 200km

  ultramafic

  sometimes referred to low velocity zone as seismic waves slow down

  temp is high enough to be close to melting temp of peridotite

  rheid

  ductile/plastic

  5% melt

  seismic waves reduce in velocity because rocks are less rigid and incompressible
• mines and boreholes


  rock at the surface can be collected and sampled

  taken to labs to analyze their chemical comp and physical properties

  mines and boreholes allow geologist to directly examine and sample rocks

  only reach so far

  project Mohole reach to mantle, reached 183m

  KTB borehole in Russia- deepest
• mines and geothermal gradient

  (-) temp and pressure increase w depth- geothermal gradient

  lord kelvin- estimate age of earth
• magmas, xenoliths and kimberlites

  normal basalt magmas at MOR made from partial melting of upper mantle

  by analyzing the composition of these magmas and their volatiles we can estimate composition

  kimberlites are volcanic rocks that occur in the earths crust in vertical structures - kimberlite pipes

  sourced deep within lithospheric mantle at depths of 250km

  erupt rapidly and violently

  carrier of diamonds and other mantle xenoliths

  by examining minerals found in these kimberlites we can analyze the composition at these depths
• ophiolites


  oceanic crust subducted and destroyed during plate collision but sometimes they are thrust up or obducted onto the continents

  sections of oceanic lithosphere can be obducted i=onto land called ophiolites

  show us what oceanic lithosphere looks like

  magma that erupts into water cools forming a basalt pillow lava

  the magma in the feeder pipe cools slower forming a dolerite and the magma left in the magma chamber cools slowly forming a gabbro
• elastic rebound for a cause of earthquakes

  1. a body becomes under stress due to opposing tectonic forces

  2. rocks distort and deform, energy stored as elastic strain energy

  3. the strength of rocks is exceeded by increasing stress and rock fractures

  4.two parts of the rock suddenly move relative to each other and there is displacement along the fault

  5. energy is released in form of seismic waves that radiate out from the source
• seismometer


  device that receives seismic vibrations, converts them into recordable signal