Origin and structure of earth

• The crust is the outermost layer of the Earth comprising about 8-40 km in depth.
• The crust is separated from the Mantle by a boundary or surface with seismic waves that change velocity, known as Mohorovičić Discontinuity. It was named after Andrija Mohorovičić, a Croatian seismologist who discovered its existence.
• Crust is the brittle outermost layer of the planet.
• The Mantle layer of the Earth composed only of molten silicate rocks. It is always in perpetual convection motion due to the core heating it.
• The mantle lies beneath the crust and extends to a depth of 2,900 km making it the thickest layer of the Earth. It is made up of very hot and dense rocks which flow due to great differences in temperature moving from the bottom to the top of the mantle, called convection currents.
• Convection Currents - Movement of magma within the mantle caused by heat generated at the core
• • The convection current acts like a conveyor belt in a factory which moves boxes. The mantle is divided into 2 sections: the upper and lower mantle, separated by the transition zone (a discontinuity between the 2 mantles).
• The core is the innermost part of the Earth. It is divided into two parts a solid inner core which is about 1,300 km and a liquid outer core about 2,250 km thick.
• • The outer core is made up of very hot liquid metals. It is composed of melted nickel and iron. The inner core, on the other hand, is in a solid state despite its very hot temperature, because of the pressure. The metals are squeezed in and are so dense that they are not able to move.
• The core also produces the Earth's magnetic field, which shields our atmosphere from charged particles emitted by the Sun.
• litho is stone
• hydro is water
• atimo is air
• bio is life
• THE CHARACTERISTICS OF EARTH THAT ARE NECESSARY TO SUPPORT LIFE

  • Water
  • Energy
  • Time
  • Recycling
• The Creation Theory - is biblical in origin asserting that everything in the universe, including humans were created by a supreme being in a span of 7 days
• The Big Bang Theory - speaks of the Earth's formation in a scientific perspective. It states that the universe is formed sometime between 10 and 20 billion years ago from a cataclysmic explosion.
• •  Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System.
• Alfred Wegener theorized that there was once a vast supercontinent 200 million years ago which he named Pangaea meaning "All-earth" and this theory is called "Continental Drift Theory " - The Theory of Plate Tectonics
• • Pangaea broke into two smaller supercontinents, called Laurasia and Gondwana throughout the Jurassic period. By the end of the Cretaceous period, the continents were separated into land masses that looked like our modern-day continents.  In 1915, Alfred Wegener published this theory in his book, “On the Origin of Continents and Oceans”.
• • There are fossil evidences which supported the continental drift theory. Eduard Suess, an Austrian geologist first substantiated that there had once been a land bridge connecting South America, Africa, India, Australia, and Antarctica. He named this large land mass Gondwanaland.
• 1. Fossils of Mesosaurus (one of the first marine reptiles, even older than the dinosaurs) were found in both South America and South Africa. These finds, plus the study of sedimentation and the fossil plant Glossopteris in these southern continents led Alexander duToit, a South African scientist, to bolster the idea of the past existence of a supercontinent in the southern hemisphere, Eduard Suess's Gondwanaland. This lent further support to Wegener's Continental Drift Theory.
• Big Bang Theory

  1. The theory suggests that the universe began from a massive blast around 10-20 billion years ago.

  2. The theory was first proposed by Belgian priest Georges Lemaitre in the 1920s, and later received support from observations by Edwin Hubble and the discovery of cosmic microwave radiation.
• Heliocentric-the sun was the center of the solar system, rather than Earth. Nicolaus Copernicus proposed the heliocentric model in his work published in 1543.
• Geocentric - the Earth is the center of the universe, with the sun and planets revolving around it.
• Nebular Theory


  The Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust
• Nebular Theory proposed by Emmanuel Kant and Laplace


  1796
• Nebular Theory


  1. Cloud collapsed

  2. Pockets of dust and gas collected into denser regions

  3. Denser regions pulled in more matter

  4. Conservation of momentum caused rotation

  5. Increasing pressure caused heating up
• The nebular theory is an explanation for the formation of solar systems. The word “nebula” is Latin for “cloud,” and according to the explanation, stars are born from clouds of interstellar gas and dust. The transition from an undifferentiated cloud to a star system complete with planets and moons takes about 100 million years. According to this theory, our own solar system formed about 4.6 billion years ago, and others are forming today in distant nebulae.
• “protoplanet hypothesis”, which essentially says that very small objects stuck to each other and grew bigger and bigger — big enough to even form the gas giants, such as Jupiter.
• Oldest radiation known


  The CMBR is the oldest radiation known to us, providing valuable information about the universe's earliest moments.
• Thermal black body spectrum at 2.725 K

  The specific thermal black body spectrum of the CMBR, meaning it emits light in a way that's similar to an idealized black body, with a temperature of 2.725 Kelvin.
• Landmark proof of the Big Bang theory

  The CMBR serves as a crucial piece of evidence for the Big Bang theory, as it is the remnant of the hot, uniform glow from the early universe.
• Also known as geosystems or physiography. Physical Geography deals with the study of the physical features of the Earth’s surface. It also deals with the different processes and patterns in the natural environment, as opposed to the cultural domain of human geography.

  Physical Geography
• studies the marine and freshwater domains of the hydrosphere. The major subdivisions include hydrogeology and physical, chemical, and biological oceanography.

  Oceanography
• cover the Earth’s outermost layer which is the crust. Major sub-disciplines of soil sciences include edaphology and pedology.

  Soil sciences
• studies the ice and icy parts of the Earth known as the cryosphere, and its effects to the environment.

  Glaciology
• studies the shape of the Earth, its reaction to different forces as well as its magnetic and gravitational fields. This study is most vital for mineral and petroleum explorations.

  Geophysics
• is the study of the earth’s rocky parts found on the crust (lithosphere) and its historical evolution. It covers lots of different disciplines of sciences such as mineralogy and petrology, geochemistry, geomorphology, paleontology, stratigraphy, structural geology, engineering geology and sedimentology.

  Geology
• deals with the study of the gaseous parts of the Earth, known as the atmosphere. The major sub-disciplines are meteorology, climatology, atmospheric chemistry and atmospheric physics.

  Atmospheric Sciences