geo midterm + finals

• Catastrophism


  Sudden, worldwide catastrophes are the agents of change that alter the physical features of the Earth over time
• Uniformitarianism


  "The present is the key to the past" - Advocates the idea that the Earth is continuously modified by geological processes that have always operated throughout time (at different rates), and that by studying them we can understand how the Earth has evolved through time
• Catastrophism was widely accepted by theologians in the early 1800s due to similarity with Biblical events such as Noah's Flood
• Catastrophism was proposed by Baron Georges Cuvier
• Uniformitarianism was proposed by James Hutton (The Father of Modern Geology)
• Compositional (Chemical) Layers of Earth

  • Crust
  • Mantle
  • Core

  
• Crust


  • Consists of several elements
  • 3 to 5 miles thick under the ocean and approximately 25 miles thick under the continents

  
• Mantle


  • Layer under the crust, comprises 82% of Earth's volume
  • About 1,800 miles deep
  • Consists mostly of silicate rocks rich in magnesium and iron
  • Heat causes rocks to rise
• Core


  • Center of the earth made of 85% iron metal and 15% nickel
  • Inner Core: Solid part of the core made of iron, has a radius of about 760 miles, hottest layer of earth at 7,000 deg C
  • Outer Core: Liquid part of the core composed of nickel-iron alloy, about 1,355 miles thick, temperature at 5,000 deg C
• Mechanical (Physical) Layers of Earth

  • Lithosphere
  • Asthenosphere
  • Mesosphere
  • Outer Core
  • Inner Core

  
• Lithosphere


  • The solid, outer part of the Earth; includes the brittle upper portion of the mantle and the crust, the outermost layers of Earth's structure; bounded by the atmosphere above and the asthenosphere

  
• Asthenosphere


  • The soft upper layer of the earth's mantle, below the lithosphere; relatively low resistance to plastic flow and convention is thought to occur

  
• Mesosphere


  • Layer below the asthenosphere but above the outer core; essentially the lower mantle; despite high temperatures, the intense pressure in this region restricts the movements of the molecules of the silicate material despite being under high temperature, thus making it extremely rigid
• Outer Core


  • Extends from the bottom of the mesosphere or the lower mantle and surrounds the inner core; extreme temperature allows metal to remain in their liquid phases; the only layer of the Earth that is true liquid; strong magnetic field is caused by convection

  
• Inner Core


  • Solidity is due to the intense pressure from the upper layers; spins at different speed than the rest of the planet, which is thought to cause the Earth's magnetic field
• Continental Drift was developed in the early part of the 20th century, mostly by Alfred Wegener
• All of Earth's continents were once part of an enormous, single landmass called Pangea, existed about 240 million years ago and began breaking up about 200 million years ago
• Other supercontinents: Pannolia formed about 600 mya, Rodinia existed more than a billion years ago
• Plate Tectonics


  Scientific theory of the large-scale motion of seven (7) large plates and movements of larger number of smaller plates; began between 3.3 to 3.5 B years ago; average tectonic plate thickness in the lithosphere is about 100 km

  
• Type of Tectonic Plates

  • Oceanic Plate - made of oceanic crust; composed of magnesium and silicon minerals
  • Continental Plate - made of continental crust; composed mainly of aluminum and silicon materials

  
• Movement of Plates


  1. Hot mantle rises at the ridge axis, creating new ocean crust

  2. The top of convention cell moves horizontally away from the ridge crest, as does the new seafloor

  3. The outer limbs of the convention cells plunge down into the deeper mantle, dragging oceanic crust, at the deep-sea trenches

  4. The materials sinks to the core and move horizontally

  5. The material heats up and reaches the zone where it rise again
• Earth Processes


  • Constructive Process - any process that builds earth material or landforms (e.g. erosion, transportation of sediments)
  • Destructive Process - any process that breaks earth material or destroy landforms (e.g. weathering, earthquakes, volcanic eruption)
• Three Geological Processes


  • Gradation - encompasses degradation (wearing down of sediments) and aggradation (accumulation of sediments)
  • Vulcanism - refers to the movements of molten rocks & the formation of solid rocks from molten state both within the lithosphere & on the surface
  • Diastrophism - refers to the movements of the solid parts of the earth resulting to displacement & deformation
• Weathering


  Breakdown of rocks at earth's surface under the influence of certain physical and chemical agencies
• Factors affecting Weathering


  • Disintegration - the process of breaking up of rocks into small pieces by the mechanical agencies of physical agents
  • Decomposition - the process of breaking up mineral constituents to form new component by the chemical actions of the physical agents
  • Denudation - term used when the earths surface is worn away by the chemical and mechanical actions of physical agents and the lower layers are exposed
• Mineral


  Naturally occurring inorganic substance of definite chemical composition and have a definite crystal form
• Physical Properties of Minerals

  • Cleavage - tendency of the crystalline mineral to break at certain definite directions, yielding more or less plane or smooth surfaces
  • Structures - mode of aggregation, the manner in which groups of crystals or mineral grains are arranged or inter-grown
  • Streak - color of the powder of a mineral as obtained by scratching the surface of the mineral or rubbing it on an unglazed porcelain surface
  • Luster - the general appearance of a mineral in reflected light (metallic luster, non-metallic luster)
  • Hardness - the resistance offered by the smooth surface of a mineral to abrasion or scratching, expressed numerically by comparison with Moh's Scale of Hardness
  • Fracture - the manner in which a mineral breaks in any directions other than cleavage direction in crystallized mineral
  • Tenacity - the property of minerals that can resist crushing, bending, or tearing or in short, its cohesiveness (brittleness, malleability, sectile, ductility, flexibility, elasticity)
  • Specific Gravity - the ratio of its weight of an equal volume of water at 4 0C
  • Magnetism - the property of the minerals that are attracted by an iron magnet
• Classification of Minerals


  • Metallic Minerals - contain metal in raw form, occur in rare, naturally formed concentrations known as mineral deposits (e.g. Bornite, Bauxite)
  • Non-Metallic Minerals - consist of stone quarries and clay and sand pits; chemical and fertilizer mineral deposits; salt deposits; deposits of quartz, gypsum, natural gem stones, asphalt and bitumen, peat and other non-metallic minerals other than coal and petroleum (e.g. Gemstones, Fluxes, Pottery Glass and Enamel, Fertilizer, Refractories)
  • Common Rock Forming Minerals - used as important tools in classifying rocks, particularly igneous rocks (e.g. Quartz, Mica, Feldspar, Olivine, Pyroxene, Amphibole, Calcite)
• Rocks are comprised of minerals, but minerals are not comprised of rocks
• Difference between Rock and Mineral

  • A mineral has a unique chemical composition and its necessarily define by its crystalline structure and shape, while a rock can be composed of several minerals and is classified according to the process of its formation
  • The commercial value of minerals is immense and rock are mined to extract these minerals, while minerals are pure and made of the same substances, but rocks are not
  • While rocks can contain one or more fossils, minerals can not
• Common Rock Forming Minerals

  • Quartz
  • Mica
  • Feldspar
  • Olivine
  • Pyroxene
  • Amphibole
  • Calcite
• The color of a rock will be determined by the proportions of light and dark-colored minerals present
• Rocks and their Related Minerals

  • Granite - Feldspar, Quartz, Mica, Calcite
  • Basalt - Feldspar, Quartz, Mica, Calcite
  • Gabbro - Feldspar, Quartz, Mica, Calcite
  • Limestone - Feldspar, Quartz, Mica, Calcite
  • Sandstone - Feldspar, Quartz, Mica, Calcite
• Rock


  A solid cumulative of minerals located in the earth's lithosphere, used by mankind through history as a basic construction material
• Types of Rocks


  • Igneous
  • Sedimentary
  • Metamorphic
• Rocks can change from one type to another over time through the rock cycle
• The rock cycle is an ongoing series of processes inside Earth and on the surface that slowly changes rocks from one kind to another
• Minerals


  • Feldspar
  • Quartz
  • Mica
  • Calcite
• Rock


  A solid cumulative of minerals located in the earth's lithosphere
• Rocks have been used by mankind through history as a basic construction material