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continental and oceanic crust is
Continental crust is thicker and less dense than oceanic crust
Our sun and solar system formed approximately:
5 billion years ago
The scientific methods includes all of the following
- Data collection
- Hypothesis formation
- Evaluation of Data
- Hypothesis testing
1.Observe an event.
2.Develop a model (or hypothesis) which makes a prediction.
3.Test the prediction.
4.Observe the result.
5.Revise the hypothesis.
6.Repeat as needed.
7.A successful hypothesis becomes a Scientific Theory.
The primary physical process that sorts the materials that make up Earth, the oceans, and the atmosphere is:
•Goal of Science?
–Discover underlying patterns in the natural world.–Use that knowledge to make predictions
•A successful theory must be repeatable.
–Cold Fusion (1989)–Ecstasy (Science, 2003)
What is the definition if a theory in scientific terms
“A model which has been born out by repeated tests and observation.”
–When hypothesis is strengthened by testing and is successful in predicting additional phenomena.
–Not a guess or hunch.
–Developed from extensive observation and experimentation.
•So: a theory is a highly successful hypothesis.
•All hypotheses make predictions.
•All theories make predictions.
•All theories can be tested.
•Result: Any scientific theory is subject to change as our ability to make tests, or make observations of a test’s results, improves with time.
•Make no predictions
•Can’t be falsified
Theories and Truth
•Science never reaches absolute truth.
•Truth is probable and based on available observations.
•New observations yield scientific progress.–Earth thought to be flat.
–Sun thought to have revolved around the earth.
Solar System Origins
•Sun and solar system formed ~5 BYA.
–Created from a cloud of gas and dust called a nebula.
–Orderly nature of solar system and age of meteorites provide evidence.
–Various stages of nebulas seen from telescopes
•Cloud of mostly hydrogen and helium revolves and its center.
•Sun is formed when magnetic fields and gravity work to concentrate particles.–Sun diameter may have equaled diameter of planetary system.
•Sun contracted leaving planetary material behind.
Very different from present Earth.
–Structure changed when heavier elements moved to core
•Bombarded by meteorites.
•Moon created by massive collision.
–Mars-size planet and protoearth collided.
–Pieces left in orbit created moon.
•Condensed into a incredibly hot, concentrated mass.
•Temps = Millions of degrees
•Hydrogen atoms form helium–Releases large amounts of energy.
–Ionized energy created solar wind.
•Energy from sun reached planets as solar radiation.
–Boiled early atmospheres (hydrogen/helium)
–Caused planet to shrink
•As planet contracted heat was produced at the core.
•Defined as mass per unit volume.
–How heavy something is for its size.
–Dry Sponge vs Wet Sponge
–Wood vs Rock
•Release of internal heat liquefied Earth’s surface.
•Elements began to segregate based on density
•High density materials (Fe and Ni) settled in the core.
•Less dense materials formed concentric spheres around the core.
Earth’s Internal Structure
•Layers defined by:
Earth’s Chemical Composition
–Low- density rock (silicate materials)
–Extends to 2885km
–Fe and Mg
–High-density, (Fe and Ni)
–Cool rigid shell
–Includes crust and upper mantle.
•Cracks with pressure
•Vertical movement of Earth’s crust
•Buoyancy of lithosphere on asthenosphere
–Less dense continental crust floats higher than denser oceanic crust
•Can flow with pressure
– 700km deep
–Extends to 2885 km.
–Made up of middle and lower mantle.
•Likely due to extreme pressure.
–Capable of flowing–Inner Core
–Does not flow due to pressure.
Origins of Earth’s Atmosphere
•During density stratification outgassing occurred
•Very different from today
•Where did the oceans come from?
–Released by volcanic outgassing from the rock within the planet.
–Came from extraterrestrial sources like comets, asteroids, or meteors.
•Why is ocean water salty?
–Salts eroded from the crust of millions of years.
–Most common form is NaCl.
•Na+ bonds with Cl-.
–Other salts: Mg, S, Ca, K, Br.
–Typical seawater is ~35ppt.
•How much salt is in the ocean?
–If dried and spread evenly, it would cover the world at a depth of 500ft.
Marine Life Origins
•What is life?
–An organic organism that is capable of metabolizing, maintaining itself, growing, responding to stimuli, reproducing, and adapting to its environment.
•Where did life come from?
–Most scientists believe it came from the oceans between 2.7
– 3.8 billion years ago.
Origins of Life
•How did it begin?
–Lightening in a chemical atmosphere.
•In 1952 Miller and Urey created an assortment of organic molecules and amino acids from inorganic compounds.
–Did not create life.
–Early atmospheric components may have been different.
Origins of Marine Life
•Why the oceans?
–Ultraviolet radiation is capable of damaging DNA of living material which often results in cell mutations or death.
–Early atmosphere had little or no oxygen in it, resulting in nothing to block the UV radiation.
–Water absorbs UV radiation allowing life to begin deep in the oceans were they were protected.
First Life Forms
•Early life forms were single celled anaerobic cyanobacteria, which got their energy through chemosynthesis.
•Oxygenic autotrophs evolved next, these organisms used light to produce energy.
•Several billion years later the autotrophs brought oxygen to their present levels.–Many species were intolerant to oxygen and went extinct, but opened room for animal evolution.
•Stromatolites are rock
-like buildups of microbial mats formed by colonies of cyanobacteria in limestone
-building communities include the oldest known fossils, dating back 3.5 billion years.
•Stromatolites are the only fossils covering the last 7/8s of the history of life on earth.
•Stromatolite communities are continuing to be discovered in Australia, the Indian Ocean, Yellowstone National Park, and the Bahamas.
•Formed by trapping and precipitating particles from microorganisms such as bacteria and algae.
•How did single celled organism lead to what we have today?
•Change as a result of individuals surviving to pass on their genes.
•A species is a reproductively isolated population that can produce viable offspring which share a common gene pool and niche.–Sexual Selection
•Peacocks, Elephant seals weighing 2x more then females.
–Periodic Mass Extinctions
•Have been at least 5, these help open up opportunities for new species.
How old is Earth?
•How do we age the Planet?
•Earth is approximately 4.6 billion years old.