Middle School Science/Earth and Space Science
Physical Geology Processes of mineral and rock formation Igneous - Magma at 600 – 1200 deg C. from 30 Km under earth (Plutonic), magma cools and crystallizes slowly within crust. Through volcanic action the magma reaches surface as lava or fragmental ejecta.
Weathering - Rocks and minerals crystallize on surface, and are transformed through chemical reactions between other minerals and conditions
Sedimentary - Compaction and cementation after deposition of either rocks by weathering and erosion (detrital), organic matter, or chemical precipitates (evaporites). Occurs at or near surface as in carbonate-rich sediments.
Metamorphic - Rock types subjected to temperature and pressure conditions different than those in which the it was formed, including previously-formed metamorphic rock. The pressure and temperature must be sufficiently high so as to change the original minerals into other mineral types or other forms such as by recrystallisation.
Methods used to identify and classify different types of minerals, rocks, and soils Classify Rocks: Hardness - 1 Talc, 2 Gypsum, 3 Calcite, 4 Fluorite, 5 Apatite, 6 Potassium feldspar, 7 Quartz, 8 Topaz, 9 Corundum, 10 Diamond
Density -- heavy gold and platinum (20), Silicates between 2.5 and 3.5, ores between 4 and 8
Cleavage -- how it breaks depends on crystal structure; some break in a predictable manner others don't. Cleavage is defined as a smooth break with a shiny surface. Cleavage can be perfect, good, or incipient. Highest cleavage can leave thin sheets; the thinnest are flakes of mica.
Fracture - When rocks are broken open, fracture surfaces are formed; fracture surfaces can be conchoidal (rounded), smooth, splintery, hackly, fibrous, even or uneven.
Twinning - appearance of fine parallel lines, called striations, on the cleavage planes. Striations change with respect to the direction it was, or is, growing.
Transparency - Can be water-clear, transparent, translucent, or opaque.
Lustre - A reflective property, not color. Can be metallic, glassy (vitreous), pearly, silky, resinous, greasy, waxy and earthy. The degree of luster is described as spleandent, shining, glistening, glimmering, matt, or dull.
Color - Natural colour such yellow for sulfur, red for cinnabar, green for malachite, or blue for azurite. Contamination in small quantities can cause changes.
Special light effects - Regularly intercalated foreign substances, by fine fractures or twinning such as Labradorescence, or Opalescence.
Streak - colour of powdered mineral on a white underlay.
Classification of common rocks - Native elements (gold), Oxides, Hydroxides, Carbonates (limestone), Sulfides (pyrite), Sulfates (gypsum), Phosphates, Halides (rock salt), Silicates (mica, clay)
The structure of the Earth and the nature of the various layers Four layers: crust, mantle, inner core, and outer core, plus the lithosphere Crust
- thinnest layer, 35 - 70 km thick on the continents, and 5 - 10 km thick under the oceans
- thinner than any of the other layers,
- calcium, sodium, and aluminum-silicate minerals.
- cold, and brittle, fractures to cause earthquakes
- 1800 miles thick
- Most of the Earth's mass
- Iron, magnesium, aluminum, silicon, and oxygen silicate compounds.
- 1000 degrees C, solid but plastic; deforms slowly with convective heat from the outer core
- 2900 miles thick and the
- liquid Fe (Iron), 3700 deg C
- 5200 km to the Center of the earth
- 4300 deg C, remains solid from pressure
- crust and the upper part of the mantle, 5 to 30 miles deep
- Earthquakes start at the lithosphere
- Earth formed with the Sun, and the other planets 4.54 billion years ago from rotating disk of dust and gas.
- Heat released from gravitational energy and radioactive decay melted planet, still cooling
- Iron (Fe) sank into the core of the Earth, lighter materials such as silicates, oxygen compounds, and water rose to the surface
Soils Three basic types: sand, silt, and clay made from finely ground rock particles, and grouped according to size Sand, the largest particle, determines aeration and drainage characteristics, Clay particles, microscopic and chemically active, bind with water and plant nutrients Ratio of particle sizes determines type.
- regolith minerals and weathered rock fragments
- humus organic matter
- living organisms
- parent rock
- relief (slope, topography)
Horizons: soil layers
- O horizon - layer of humus on the ground surface
- A horizon (zone of leaching) - Top soil with rich organic matter, usually has dark color
- B horizon (zone of accumulation) - Subsoil, may contain soluble minerals such as calcite in arid climates (caliche)
- C horizon - Weathered bedrock or saprolite (chemically weathered rotten rock)
- Bedrock - lies below the soil profile
- Pedalfer - humid climates, rich in Al and Fe
- Pedocal (caliche) - arid climates such as in the Southwestern U.S; called caliche (or hardpan) it is a calcium carbonate deposit
- Laterite - tropical climates with very high rainfall iron and aluminum oxides, all other elements virtually depleted It is derived from the weathering of basalt in high rainfall conditions, which has caused leaching of elements and nutrients. When used for agriculture, the small amount of nutrients is quickly depleted, and the soil dries to become as hard
- Bauxite - Rich in Al oxides, intense tropical weathering depletes of nearly all other elements. Derived from weathered of granite; the more soluble Ca, Na, K, and Si have been leached leaving Al. It is the principle ore of aluminum.
- Loam - farm soil; sand, silt, manure, and clay with humus
- Humus - organic soil material that has broken down to a point of stability that will not change if conditions don't. In agriculture it means compost.
Internal processes and resulting features of the Earth, including folding, faulting, earthquakes, and volcanoes
- Folding - the bending of rocks from compressional tectonic forces such as continental collisions.
- Faulting - fracturing of rock structures causing breakage and slip that is parallel to the fracture. The rocks have been subjected to compressional, extensional, and shearing forces; and they are found close to surface of the Earth.
- Earthquakes - release of elastic strain energy that radiates seismic waves. It causes the movement of faults, and creates planar zones of deformation within upper crust. Highest stress most often found at the boundaries of the tectonic plates / volcanic regions and anthropogenic sources
- Volcanoes - magma erupts through the surface often occurs near the boundaries of the continental plates
Plate tectonic theory and the evidence that supports this theory
Major plates African, Antarctic, Australian, Eurasian, North American, South American, Pacific, Cocos, Nazca, and the Indian plates
- continental drift
- sea-floor spreading
Motion - Lithosphere is rigid, and asthenosphere is plastic. Convection currents in the mantle are transmitted through the asthenosphere; and the motion is driven by friction between the asthenosphere and the lithosphere. Since continental and oceanic lithospheres differ appreciably in thickness, the effects are proportionately different.
Boundary zones - earthquakes and volcanoes; mountains and oceanic trenches.
Types of Boundaries
- Transform boundaries plates grind past each other along transform faults
- Divergent boundaries (oceanic rifts) plates slide apart from each other.
- Convergent boundaries (active margins) where two plates slide towards each. Either one is pushed down, a subduction zone, or there is collision and compression forming an anorogenic belt
Other forces in plate motion:
Trench suction - Local convection currents pull down on plates in subduction zones at ocean trenches.
Gravity - Ridge-push, plate motion driven by higher elevation of plates at mid-ocean ridges, slides downhill / higher elevation caused by low density of hot material upwelling in the mantle
Slab-pull -Plate motion is driven by weight of cold, dense plates sinking into the mantle at trenches strongest force directly operating on plates / trench suction plays important role / driving force and its energy source are still debatable subjects
Water: the hydrologic cycle and the processes by which water moves through the cycle The Earth's Water Budget - the distribution of water among the oceans, land and atmosphere.
Evaporation (evapotranspiration) - water forms into a gas and rises into the atmosphere from solar radiation, some comes from plants (transpiration), most comes from oceans.
Condensation - Vapor forms into liquid and possibly solid within the atmosphere to produce clouds and fog
Transport (advection): The movement of water through the atmosphere, water storage in the atmosphere
- convection in unstable air
- atmospheric motions in the vertical direction
- associated with cyclones
- lifting of air by fronts
- lifting over elevated topography such as mountains
Precipitation - The transfer of water from the atmosphere to land. Rain, snow, hail, sleet, and freezing rain are discussed
Foliage (canopy) interception - Precipitation intercepted by plants re-evaporates into the atmosphere
Infiltration - Water is stored in the ground
Runoff - Rivers, lake, and streams transport water from land to the oceans. Too much rainfall can cause excess runoff, or flooding
Groundwater - located below ground and how it returns to the surface
Sub-surface flow - Water may return to the surface, or flow to the oceans
Weathering, erosion, and deposition
Weathering - the decomposition of rock.
Erosion - the displacement of solids (soil, mud, rock, and so forth) by the agents of wind, water, ice, movement in response to gravity, or living organisms
Deposition (sedimentation) - the process by which material is added to a landform, by which wind, water, or ice create a sediment deposit through the laying down of granular material that has been eroded and transported from another geographical location.
Uniformitarianism -- geologic processes same all through time, past geologic events can be explained by phenomena and forces of today.
Basic principles of stratigraphy - study of rock layers, sedimentary and layered volcanic rocks
- Sequence, spacing, composition, and spatial distribution of sedimentary deposits and rocks
- Geology reconstructs the history of the Earth
- Geologic processes that change the Earth's surface and subsurface
- used with structural geology and paleontology to tell the sequence of events
- evolution of plants and animals
- radiometric dating derives absolute versus relative ages of geologic history
Lithologic stratigraphy - study of sedimentary and layered volcanic rocks, where the lowest layers are the oldest
Superposition -,the oldest strata occur at the base of the sequence in an undeformed stratigraphic sequence,
Chemostratigraphy - relative proportions of trace elements and isotopes within and between lithologic units
Cyclostratigraphy - relative proportions of minerals, carbonates and fossil diversity related to changes in palaeoclimates (cyclic)
Biostratigraphy (paleontologic) - fossil evidence in the rock layers / Strata from widespread locations containing the same fossil fauna and flora are correlatable in time
Relative and absolute time
Relative time (chronostratic) - relative age relationships (most commonly, vertical/stratigraphic position). These subdivisions are given names, most of which can be recognized globally, usually on the basis of fossils.
Absolute time (chronometric) - numerical ages in "millions of years" or some other measurement. These are most commonly obtained via radiometric dating methods performed on appropriate rock types.
Formation of fossils
Permineralization - pores of the plant or animal remains are impregnated by minerals / original shape not changed.
Casts and molds - fossils where the organisms shape has been impressed onto rocks
Impressions - two dimensional imprints of an organism which contain no organic matter.
Whole organism preservation - petrified forest; eggs of dinosaurs, by desiccation or freezing
Types of information fossils provide Both animals and plants
- past environments
- evolution, and extinction
- determining ages of rocks in which fossils are found
Geologic time scale and how it was developed Phanerozoic (544 million years ago to present), includes Paleozoic, Mesozoic, and Cenozoic eras
- era of abundant animal life
- 545 million years ago to present
- starts with diverse hard-shelled animals
Paleozoic (542 mya to 251 mya)
- begins with hard shelled fossils
- sophisticated reptiles and modern plants develop
- dinosaurs became extinct at end
Mesozoic Era (248 to 65 million years ago)
- created modern life
- continents drifted apart
- warm climate and rifting influenced evolution
Cenozoic Era (65 million years ago to present)
- continents moved to their present positions
- co-dependent flowering plants and species
- mammals become dominant species
Precambrian (4500 to 544 million years ago) includes Proterozoic, Archaen, and Precambrian
Proterozoic Era (2500 to 544 million years ago)
- 90% of all geologic time
- continents first appeared /
- bacteria and archaeans as oldest abundant fossils ,
- eukaryotic cells appear 1.8 billion years ago
Archaean Era (3800 to 2500 million years ago)
- earliest life, bacteria microfossils,
- reducing atmosphere of methane, ammonia, and other gases
Hadean Time (4500 to 3800 million years ago)
- Solar System was forming
Geologic time was developed when after fossils are found buried in a definite order
Outline the sequence of important events in the Earth’s history
- First human beings 1 mya
- Ice Age 2 mya
- Mass extinction (destroyed dinosaurs and many species of marine life) 65 mya
- First flowers 136 mya
- First mammals and birds 200 mya
- First dinosaurs 210 mya
- Mass extinction (destroyed 75% of all marine species on planet) 225 mya
- First reptiles, trees and insects 330 mya
- First land plants, first amphibians 395 mya
- First fish 400 mya
- Oldest life forms on Earth 3400 mya
- Formation of Earth 4600 mya
Precambrian 650Ma - The Late Precambrian was an "Ice House" World, much like the present-day.
Cambrian 514ma - Animals with hard-shells appeared
Ordovician 458ma - coldest times in Earth history
Silurian 425ma - Coral reefs expand and land plants begin to colonize the barren continents
Devonian 390ma - Freshwater fish migrate from southern hemisphere continent to North America and Europe. Forests grew for the first time in the equatorial regions of Artic Canada.
Early Carboniferous 356ma - Paleozoic oceans between Euramerica and Gondwana began to close
Late Carboniferous 306ma - Euramerica and Gondwana began to close, forming the Appalachian and Variscan mountains / ice cap grew at the South Pole / four-legged vertebrates evolved
Permian 255ma - deserts covered western Pangea / reptiles spread across the face of the supercontinent. 99% of all life perished at end of the Paleozoic Era.
Triassic 237ma - supercontinent of Pangea allowed land animals to migrate from the South Pole to the North Pole. Life began to rediversify / warm-water faunas spread across
Jurassic 195ma - south-central Asia had assembled, Pangea begins break up
Late Jurassic 152ma - Pangea break apart Middle Jurassic / Late Jurassic Central Atlantic Ocean narrow ocean separating Africa from eastern North America. (Africa) Eastern Gondwana separate form (South America) Western Gondwana
Cretaceous 94ma - India separated from Madagascar
K/T extinction 66ma - comet global climate changes killed the dinosaurs / oceans had widened
Eocene 50ma - India collide Asia Tibetan plateau / Australia move rapidly northward.
Miocene 14ma - Antarctica was coverd by ice and the northern continents were cooling rapidly.
Last Ice Age 18K - "Ice House" climate mode, there is ice at the poles; polar ice sheet expands contracts variations in the Earth's orbit
Modern World - Global climate is warming / new Pangea supercontinent forming
Formation and movement of ocean waves Wind blows across the smooth water surface, the friction or drag between the air and the water tends to stretch the surface, resulting in wrinkles surface tension acts on these wrinkles to restore the smooth surface
Tides: causes and factors Gravitational pull from the Moon and Sun; the force increases and decreases with changing distance of the Earth from them.
Major surface and deep-water currents in the oceans and the causes of these currents Surface currents 10% of ocean water, 400 meters deep Deep currents gravity driven because of differences in salinity and temperature, colder northern air causes temperature decreases and hence sinking
Forces: Primary - starts water moving Secondary - influence direction of currents
- Solar Heating - warming water rises at equator and sinks in northern waters
- Winds - Long term winds will driver water 2% of wind speed
- Gravity - Sea slope, surface 8 cm higher at equator from expansion causing a slope, and density
- Coriolis - Controls direction of large streams
Topography and landforms of the ocean floor and shorelines
Continental Shelf - a few hundred feet deep with an average width of 70 kilometers (43 miles), gentle slope
Continental Slope and Rise - starts with shelf break beyond which slope increases to 4° slope. Average width of 16 kilometers (10 miles), and descends to 2.4 kilometers (1.5 miles)
Abyssal plain (no light) - where the continental rise ends has an average depth 4 kilometers (2.5 miles)
Abyssal hills - small extinct volcanoes all over abyssal plains; flat-topped hills are submerged islands.
Mid-Ocean Ridge - undersea mountain chain along the middle of the ocean where plates are being pulled apart
Rift Valley - deep depressions along the center of the mid-ocean ridge whose sides are faults; hot material is constantly being extruded from Earth's mantle
The physical and chemical properties of seawater Freezing 1.910 °C / Boiling 100.56 °C
Components of Seawater Litre H2O
- Oxygen 857.8g
- Hydrogen 107.2
- Chloride (Cl-) 19.0
- Sodium (Na+) 10.5
- Sulfate(SO4-) 2.7
- Magnesium (Mg2+) 1.3
- Calcium(Ca2+) 0.4
- Potassium(K+) 0.38
- Bicarbonate(HCO3-) 0.14
- Trace elements (0.52 g)
- Nutrients (trace elements) Phosphate (PO4)
- Nitrate (NO3)
Source of salts (ions) - Weathering, hydrothermal fluxes, dissolution from crust, and volcanic eruptions,
Nutrient cycles of the ocean Nutrients
- phosphates (PO4)
- nitrates (NO3)
- Ammonia (NH4)
- Silica (SiO2)
Photosynthesis or Chemosynthesis (produces oxygen) - 6CO2+6H2O+energy=C6H12O6+O2 Respiration - C6H12O6+O2=6CO2+6H2O+energy
Nitrogen Cycle - Compounds: N2, NO3, NH3
- Nitrates enter the oceans from the atmosphere and rivers
- Bacteria and plants absorb these and form carbohydrates and ammonia
- Other bacteria and animals breakdown carbohydrates and recycle nutrients
- Nutrients are rapidly used and recycled in the marine environment
Structure of the atmosphere and thermal and chemical properties of atmospheric layers
Troposphere - to 10km, layer closest to the planet, has largest percentage of the mass, much vertical mixing from the radiation of solar heat absorbed by the Earth's surface. Temperature deceases with height.
Stratosphere - between 10 and 50 km / temperature increases with height
Ozone layer - or ozonosphere, within stratosphere
Mesosphere - 50 km to 80 km, temperature decreases with height
Thermosphere - 100-200 km nitrogen and oxygen / temperature increases to 1500 K
Ionosphere - lower thermopshere; has particles that are ionized by the sun; responsible for auroras , the region containing ions: approximately the mesosphere and thermosphere up to 550 km.
Exosphere - 1000 km where the atmosphere thins out into space; has free moving particles that may migrate into the solar wind or down into the lower layers.