Science OGT Study Guide - Tri-Village High School



Science OGT Study Guide

Earth & Space Science

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Big Bang Theory

Theory that the earth was created in one giant explosion billions of years ago, and is constantly expanding today from this location.

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Evidence of the Big Bang Theory – red shift

Red shift: displacement of a star’s light toward the red end of the spectrum, caused by an increase in distance from the star and the observer.

*The light most galaxies give off is close to the red end of the spectrum because as they move farther out, the energy becomes weaker and stretched out. This light energy is longer and the color is RED.

How a star is formed

Nebula: a cloud of dust and gas that are pulled together by gravity.

The gravity produces great heat, when hot enough, nuclear fusion occurs which causes hydrogen protons to join together producing the massive energy just as our sun does.

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Earth’s position in the Solar System

Geocentric Theory: earth is the center of the solar system- WRONG

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Heliocentric Theory: Copernicus proposed that the sun is the center of the system.

CORRECT! Earth & other planets orbit the sun.

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Law of Universal Gravitation

-Between any two objects there is an attraction (gravity) that is proportional to the mass of the objects and the distances between them.

-Our sun is more massive than the planets so they revolve around the sun.

-Earth is more massive than the moon, so the moon revolves around the earth.

-Less massive objects still provide a pull (force) on more massive objects.

-The moon has strong enough gravity to pull on water from the oceans- this is why we have tides: twice daily rise and fall in the water level of Earth’s oceans.

History of Earth

• Began with a nebula

• Early earth had lots of volcanoes

o gas from volcanoes made first atmosphere

• cyanobacteria- first life on earth

o Lived in oceans, performed photosynthesis and released oxygen which helped put oxygen into the atmosphere.

Learn about the history of Earth by studying rocks and fossils.

• Fossils can be used to match up rock layers that are far apart.

• Matching rock layers

Geologic Time Scales

Relative Time Scale: determine age by the sequences of rocks.

Ex. oldest rock would be found on bottom, youngest rock on top. [pic]

Absolute Dating: actual dates and ages

Ex. Radiometric dating

• Some rocks contain elements with unstable isotopes that decay slowly over time. They will decay into a different element that is stable. This change occurs at a rate called a half life- amount of time required for half a sample of the radioactive isotope to decay.

o Can use this to determine the age of the Earth.

Plate Tectonics

Convection Currents Mantle Core Crust

Diagram of the Earth

Effects of Plate Tectonics: plates move & interact to

produce different results.

• Alfred Wegener proposed the theory of

Continental Drift – continents are drifting across

Earth’s surface.

o based on how the continents fit together like pieces of a puzzle.

o Evidence: Matching fossils found on different continents.

• Sea-floor spreading: new ocean crust is created at mid-ocean ridges as older crust moves away.

Mid-ocean ridge: underwater mountains that extend into all oceans.

• Subduction Zone: when an ocean plate collides with a continental plate, the ocean plate tends to slide under the continental plate & forms a subduction zone.

• Mountain Ranges: occurs when Earth’s plates collide and push up.

• Earthquakes: when one plate slides past another

• Volcanoes & islands: hole in crust, magma rising up from earth’s interior to the surface

o Example: Hawaiian Islands

• Folding & Faulting: movement of plates can cause rocks to bend, fracture, and slide.

Plate tectonics: theory that Earth’s crust is broken up into a number of large plates that move & interact.

Convection Currents: transfer of heat by the flowing action within a liquid or gas- heat rises, cool sinks. (Moves the plates)

Mantle: Thick layer of rock below

Earth’s crust; it is solid, but flows very slowly

Core: Earth’s center

Crust: Outermost solid rock layer

Example: Glacial deposits would be the youngest rock and Granite would be the oldest rock

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