Part 1 Composition And Structure Of The Earth

Part 1 COMPOSITION AND STRUCTURE OF THE EARTH PLANET FORMATION AND INTERIOR OF THE EARTH 1 How planets are formed?? Universe began as a hot and infinitely dense point ca...

Part 1 COMPOSITION AND STRUCTURE OF THE EARTH PLANET FORMATION AND INTERIOR OF THE EARTH 1 How planets are formed?? Universe began as a hot and infinitely dense point called Singularity THE BIG BANG MODEL 13.8 billion years ago this tiny singularity violently exploded (Big Bang) Matter, energy, time and space created mm size Similar to a supercharged black hole 2 3 How are planets formed?? SOLAR NEBULA HYPOTHESIS Solar nebula is a large, rotating cosmic cloud of interstellar dust and gas Comprised of hydrogen and helium created shortly after Big Bang and heavier elements ejected by supernova Pillars of Creation by James Webb Materials coming from Supernova and cosmic gases, planets evolved through accretion 4 5 Accretion Present day accretion (Meteor showers) 6 How planets are formed?? The ices are especially abundant in the outer part of the solar system where the giant planets form Silicate–oxide particles are concentrated in the inner part and give rise to the terrestrial planets 7  The Cosmic Timeline Ba: Billion Annum 13.8 Ba : Big Bang – The universe created. Since then First 400,000 years: No significant event, universe was a dark, hot and dense Next 200 – 300 Ma: H2 and He gases generated and fused into first stars First light to the universe No metals in the universe Galaxies appeared (1 Ba from the big bang) 6Ba from the Big Bang: Super Novas Nickel, Silver, Gold, Lead elements came into the existence 9Ba from the Big Bang: The Milky way formed 4.6 Ba from today: The Earth and The Sun formed 8 Interior of the Earth 9 Interior of the Earth CONCENTRIC LAYERS OF THE EARTH Earth interior can be explained by two different views Lithosphere Crust Asthenosphere Mantle Mesosphere Core Outer core Inner core 10  Two Types of Crust Si, Mg Si, Al Composition of the crust: oxygen, silicon, aluminum, calcium, iron, sodium, potassium, magnesium Interior of the Earth Lithosphere Asthenosphere Composed of both the Partially molten upper crust and the portion of mantle material that the upper mantle that behaves plastically and behaves as a brittle, rigid can flow solid 12 Interior of the Earth MANTLE 2900 km thick, 67% of Earth's mass Composition: more iron, magnesium, less aluminum and somewhat less silicon than the crust In terms of volume, the largest of Earth's three chemical layers Physical conditions in mantle change because pressure and temperature increase with depth Temperature ranges from 870 °C to 2200 °C 13 Interior of the Earth CORE Innermost layer of the earth, mainly metallic, Mostly comprised of iron and nickel 6800 km in diameter (3400 km from outside edge of core to center of core) 1/3 of Earth's mass, 15% of its volume Temperature ranges from 2000 °C to 5000 °C Consist of 2 parts INNER CORE OUTER CORE Physical state – solid Physical state – liquid Density – 9.9-12.2 g/cm3 Density – 12.6-13 g/cm3 Composition – metallic: 95% Fe, 5% Ni Composition – liquid Fe and Ni Temperature - 4500 °C and 5500 °C Temperature - 5200 °C 14 Interior of the Earth CHEMICAL COMPOSITION OF THE EARTH Approximately 90 % Fe + O + Si + Mg+Al Other elements Ni, S, and Ti 15 How can we see the interior of the Earth? Direct evidence from rock samples Indirect evidence from seismic waves 16  Study the Earth's interior SEISMIC OR EARTHQUAKE WAVES Body waves – Travel through Earth’s interior. They are important in determining the Earth’s interior Primary waves (p waves) ( 6 km/s) Secondary waves (s waves) ( 4 km/s) Surface waves – They travel along the surface of the Earth or along discontinuities in the Earth Love waves 17 Rayleigh waves  Study the Earth's interior Crust Mantle PROPAGATION OF SEISMIC WAVES THROUGH THE EARTH Core Crust (Solid) Reflection Mantle (Semi-Solid) Refraction Outer Core (Liquid) Shadow Zones Inner Core (Solid) 18 Geologic time scale Precambrian Part 2 Plate Tectonics 20  Plate Tectonics Earth’s crust broken in to 20 pieces approximately. Why? 6 large plates There are small pieces They move on the Asthenosphere. Movements create new and destroy existing plates Pieces are called Plates Tekton in Greek is for “Builder” Building of Plates – Plate Tectonic Plates interact with each other along the Margins of Plates (Plate Boundaries) (ie. Plate Tectonics) Earthquakes & Plate Boundaries Volcanoes & Plate Boundaries  Volcanoes & Plate Boundaries There is a relationship between earthquakes, plate tectonics, volcanoes. How fast are the plates moving? Plates move 1-10 centimeters per year (≈ rate of fingernail growth). Plate Boundaries in Iceland Plate Boundaries Divergent Plate Boundary Plate Boundaries Convergent Plate Boundary Plate Boundaries Transform Plate Boundary  Divergent Transform Convergent Andes Peru-Chile Trench Plate Boundaries – Possible Activities Convergent Boundaries – Subduction Zones Oceanic-Continental Convergence Oceanic crust is denser, subducted, or forced under the less dense continental crust. Continent-Continent Convergence Both plates have the same density. Colliding edges are crumpled and uplifted, producing mountains (Orogeny). Oceanic-Oceanic Convergence One plate forced under the other Descending plate subjects to melting Trench/volcano/island arc Plate Boundaries – Landforms Divergent Boundaries Plate Boundaries – Landforms Sea floor spreading New sea floor is created Subduction New ocean floor is created is consumed at the subduction zones The lithosphere sinks under the asthenosphere. Trench/Volcano!  Interesting Evidences/ Observations Continents’ shapes Similar geology/Mountain Ranges Fossil evidences Climatic patterns Paleomagnetism Interesting Evidences/ Observations Interesting Evidences/ Observations Mesosaurus Interesting Evidences/ Observations Climatic Patters – Glacial Deposits Climatic Patters – Deserts Continental Drift Based on the observations of Continents’ shapes Similar geology/Mountain Ranges Fossil evidences Climatic patterns German climatologist Alfred Wegener proposed the “Continental Drift Theory” in 1915 He proposed the continents had formed a single mass, called Pangaea (Greek for "all the Earth"). Pangaea had rifted, or split, and its pieces had been moving away from each other ever since. He believed that Pangaea originated near the south pole centrifugal force of the planet caused the protocontinent to break apart and the resultant continents to drift towards the equator. It is the Continental Drift Theory 1880 - 1930  The supercontinent “PANGAEA”, which means “all Earth” A New Theory! Continental Drift Continental Drift - Paleomagnetism In the 1950's that magnetically aligned iron-rich minerals in lavas froze during cooling was understood. The apparent position of the magnetic north pole over the past 500 Ma showed that either the magnetic poles migrated through time or that the lava flows had moved, and the continents had drifted (Polar Wondering). Bernard Brunhes discovered paleomagnetism in 1906 Seafloor Spreading Harry Hass in 1962 hypothesized that the Seafloor move away from the crest of the mid-oceanic ridge as a result of mantle convection. Seafloor moves as a conveyor belt at 1- 24 cm per year 1 1 – Oldest – Earliest formed crust 2 – Younger – later formed crust 3 – Youngest – Newly formed crust 1 2 1 1 2 3 2 1 Sea Floor Spreading – Age Evidences Recent Evidence for Continental Drift Best fitting along the middle of the continental slope rather than constantly changing coastline Matching Geology with modern techniques Degree of Metamorphism Similarities in Isotope Age Continental Drift Wagener’s hypothesis together with Hass’ Hypothesis is accepted now for explaining Continental Drift. These two hypothesis were later supported by many observations and data Now these hypotheses are explained as Plate Tectonics Theory Prat 3: Rocks, Structures and Weathering Minerals Naturally occurring homogeneous inorganic solid of definite internal atomic structure Rocks  Rock Types Igneous Sedimentary Metamorphic From Lava or Magma From Sediments From any existing rocks 1. Soil or 2. Sand Temperature/ Cooling 3. Washing/wearing out of rocks 4. Chemical precipitation Pressure and 5. Bio materials Volcanic or Plutonic Temperature Temperature and Pressure Textures and Features Compaction, Lithification, Metamorphic Diagenesis, Cementation rock Rock types Clastic – Chemical - Biogenic 1. Based on composition 2. Based on origin Different grades Textures and features Igneous rocks Yosemite Granit Batholith Plutonic rock Volcanic rocks Sedimentary rocks Clastic Sedimentary Rocks Chemical Sedimentary Rocks Calcareous Siliceous Evaporites Biogenic Sedimentary Rocks  Process of Sedimentation Digenesis and Lithification Chemical Precipitation 58 Metamorphic rocks  Sandstone → Quartzite Shale → Gneiss Limestone → Marble Parent Rocks 62 Rock Cycle Geology of Sri Lanka Line of hot water Springs Deformation & Geologic Structures Primary Structures Stress – Strain - Deformation Deformation – Change in shape due to applied stress (or change in Temperature) Strain - The ratio of the deformation to the original length Deformation has units (of Length), Strain is unitless Deformation and stress express the similar process Brittle Structures Ductile Structures Anticline – Antiform Syncline - Synform Fold Axis Axial Plain  Foot wall Hanging wall Normal Fault  Foot wall Hanging wall Reverse Fault Strike-slip Fault/ Transform Fault Horst and Graben Fractures and Joints Weathering is the response of rocks and minerals which were within the lithosphere to conditions at or near the atmosphere, the hydrosphere, the biosphere. Weathering operates when end product (soil) is more stable at the surface conditions (Reiche, 1950). Weathering What does it give?  What does it give? Rock weathering Process of breaking down rocks into soil Why? 84 At Omiya Koen Station Types of Weathering Disintegration Frost wedging Frost heaving Unloading Exfoliation Spheroidal weathering Decomposition Chemical weathering (water, oxygen and acids) Carbonation Hydrolysis Oxidation Biological weathering Types of Weathering Weathering mechanisms Freeze and thaw Physical/Mechanical weathering (Disintegration) Types of Weathering Weathering mechanisms Physical/Mechanical weathering (Disintegration) Freeze and thaw Exfoliation – Heat and cool Chemical weathering (Decomposition) Oxidation Eg Fe+2→ Fe+3 87 Types of Weathering Chemical weathering Carbonatio Dissolution n Rocks Limestone dissolve by dissolution water (Not by acids necessarily by Ocean water) Hydrolysis Hydration Feldspar + water → Clay Water absorbing in to existing minerals 88 Gypsum (CaSO4.2H2O)  Biological weathering Roots Lichens Bacteria Human 89 Soil Profile Degree of Weathering Soil Completely Weathered Rock Moderately Weathered Rock Slightly Weathered Rock Fresh Rock