Earth Systems 3209/Earth Science 1000 (MUN) Midterm Review
What is Earth Science?? • Earth Science differs from other sciences in that: • Earth Science has a global perspective • Earth Science draws from all other areas of science 3. Earth Science requires a consideration of vast amounts of time
4 Major Branches of Earth Science • Geology: examines earth, its form and composition, and the changes it has undergone and is undergoing. • Meteorology: study of the atmosphere and atmospheric phenomena; weather and climate. • Astronomy: study of the universe; it includes the observation and interpretation of celestial bodies and phenomena. • Oceanography: study of the oceans and oceanic phenomena.
Evidence, Theories, ParadigmsScientific Knowledge • Evidence – facts collected by observation and measurement which serve as a springboard for development of theories • Hypothesis: Is a tentative or untested explanation to explain how or why things happen in an observed manner. • Theory: A well tested and widely accepted view that explains certain observable facts. • Paradigm: Is a theory that that is held with a high degree of confidence with a lot of evidence. • Law: A formal statement summarizing observations of natural phenomena occurs under given conditions.
Formation of the Universe • Creationism (considered a Non-Scientific View): • Belief in the bible, other holy texts or spoken word that led to the idea that Earth was created by a creator with purpose
Big Bang Theory • Proposes that universe originated as a single mass that exploded around 15 billion years ago. (best estimate is 13.7 bya) • After a few billion years material cooled and condensed into stars and galaxies. • The explosion caused continuous expansion so galaxies moved away from one another. • About 5 bya our solar system formed within the Milky Way galaxy • Expansion and cooling continues.
Solar Nebular Hypothesis pg.19,628 • Explains the formation of the solar system which began about 5 bya (at least 10 by after the Big Bang occurred)
4 stages of Solar Nebular Hypothesis • Nebula Huge rotating cloud of dust and gas contracts due to gravity to form a “nebula”
4 stages of Solar Nebular Hypothesis 2. Protosun • Most material is gravitationally swept toward the centre • Material is concentrated at the center to form the protosun (presun)
4 stages of Solar Nebular Hypothesis 3. Protplanets • As temperatures dropped, substances with rock forming minerals (iron and nickel) joined together while orbiting the sun. • Repeated collisions over millions of years formed the planets.
4 stages of Solar Nebular Hypothesis 4. Solar Systems • Remaining debris was either collected into the planets and moons or swept into space by solar wind.
STSE • Remember: • Universe Vs. Solar System • The Universe: incorporates several solar systems. • A solar system: is represented by planets orbiting stars. • Habitable Zone (Goldilocks zone) • This zone in a solar system is where liquid water can exist on the surface and not too far from the star it is orbiting (too cold) or too close to the start it is orbiting (too hot). Just right!
STSE • If you can find planets orbiting stars (other than the sun), then you have found a solar system. • There have been 1500 solar systems found to date. • Five Methods for Finding Solar Systems • Radial Velocity Method • Transit Photometry Method • Astrometry Method • Microlensing Method • Direct Imaging
STSE • Transit: The passage of a planet between a star and the Earth. • Extrasolar planets: Planets that exist in other solar systems (as opposed to the solar system where Earth exists). These are called exoplanets.
STSE • The Solar Nebula Hypothesis infers that a solar system should have rocky inner planets and larger gaseous planets much further out. • Many solar systems found do not fit the pattern described above. • Maybe gravity and friction has caused the larger planets to move. • Alone, the “Solar Nebula Hypothesis” seems too simplistic. Maybe it just represents the formation and configuration of early planets.
Origin of the earth • It was thought that Earth was not always layered as it is today. Some scientists suggest that Earth was somewhat like the moon billions of years ago
Why does earth have layers? • Thanks to nature (i.e. heat and gravity) • Sources: • Radioactive Decay • Particle Collisions • Residual Heat Related to density This process is often referred to as differentiation or segregation. *still occurring today (smaller scale)
Crust Lithosphere • State: Thin, rocky outer skin • *Roughly 100km think (varies depending on ocean or continental) -
Asthenosphere (upper mantle) Mantle State: Mainly solid, very strong but can flow (like silly putty or an eatmore bar) *Is 2900 km thick – The thickest layer!
Outer Core • State: liquid • Composition: iron and a small amount of nickel • * 2270 km thick • - convection currents exist within and contributes to origin of magnetic field
Inner Core *Hotter, denser and stronger that outer core **State: solid Radius = 1216 km
Temperature and Density Increases with Depth Temperature and Density Increases with Depth • Density inside Earth increases as depth inside Earth increases. • Temperature inside Earth increases at a rate of approximately 35 degrees celcius per kilometer. This is referred to as the Geothermal Gradient.
Hydrosphere Biosphere Geosphere Atmosphere
Order of development • Geosphere hydrosphere atmosphere biosphere • Hydrosphere and atmosphere formed from early “outgassing”, where molten material cooled and released dissolved gases into the atmosphere (N2, H2O vapor, CO2, Ar)
The earth is a complex set of interacting systems • Each sphere influences one another and effects our daily lives
All 4 Spheres • Shoreline
Catastrophism • Is a concept popular in the 1700-1800’s which states that earth’s landscapes had been shaped primarily by great disasters or catastrophes (floods, storms, earthquakes, volcanic eruptions etc.) • James Ussher:Anglican Arch Bishop and scholar attempted to fit the rate of change of Earth processes into a relatively young aged Earth. ** Unknown causes which were fast
James Hutton • Scottish Geologist after years of studying landforms and rocks • “ the present is the key to the past” and • “that, the physical, chemical, biological laws that operate today to shape Earth also operated in the past.”
Uniformitarianism • two key concepts; 1) the geologic processes at work today were also active in the past. 2) the present physical features of Earth were formed by these same processes, at work • over long periods of time.
Absolute time • Identifies the actual date of an event, & pinpoints the exact time in history when something took place. • For example, the extinction of the dinosaurs about 66 million years ago and the age of • Earth is approximately 4.6 Billion years.
. Relative time • Attempts to place events in a sequence of formation, but does not identify their actual date of occurrence. • Comparing events to each other often does this. • Can’t tell us how long ago something happened; only that it followed one event and preceded another.
relative dating 6 Major Types: • Superposition • Horizontality • Cross-cutting relations • Inclusions • Unconformities • Fossils
1. Law of Superposition • Book and cylinder demos • In an undeformed sequence of sedimentary rock, each bed is older than the one above and younger than the one below. *The youngest is always on top
2. Principal of original Horizontality • states that most layers of sediment are deposited in a horizontal position. • If rock layers are folded or inclined, then the layers must have been moved into that position by crustal disturbances. (folding/faulting)
Faulting and Folding • Faulting – Movement of rock units along a crack in the rock. • The fault below is caused by compressional forces.
Faulting and Folding • Folding – Bending of rock units caused by compressional forces, as seen below.
3. Cross-cutting relations • Book demo • An igneous rock is younger than the rock strata (or beds or layers) that it cuts across. • A geological feature such as a fault is younger than the rock strata (or beds or layers) that it cuts across.
Contact Metamorphism • When molten rock comes into contact with older rock • the heat causes a kind of baking that changes the original rock. • Often represented as x’s on diagrams
4. Law of Inclusion fragments (rock fragments) • Pieces of one rock found in another rock must be older than the rock in which they are found.
5. Unconformities A surface between successive strata (layers) representing a missinginterval in the geologic record of time 3 types: • Angular Unconformity, • Disconformities and • Nonconformity
6. Fossils - Correlation • Hand out fossils • Fossils are used to match up rock layers between widely separated areas or between continents • any time period can be recognized by its fossil content. • the matching up of rock layers from one area to another.
Interpreting and Drawing well-labelled, detailed cross-sectional diagrams (Lab) • in order to do these, rock types need to be correlated based on color, texture, rock types and fossils. • Examples – a key is needed
Absolute Dating - pg. 228-235 • Is finding the exact age of a mineral, rock, fossil, landform or finding exactly when a geological event occurred. • 3 Ways • Tree Growth Rings • Varves - Glacial deposits • Radiometric dating • ALL PRODUCES NUMBERS!
Tree Growth Rings • 1 Growth Ring = 1 Year • In places where seasonal changes occur (e.g. Newfoundland), plants add on a new growth ring each year. • By simply counting the growth rings in a tree, one can calculate its age.
Varves • Are seasonal deposits of sediment that show alternating layers of clay and sand. • Dark fine layer is deposited in fall/winter when lake is frozen and humus settles out of water. (clay) • Light coarse layer is deposited in spring/summer due to abundant meltwater carrying large sediment loads (sand) 1 layer of light and dark (2 sediment layers) = 1 year