Earth Science CA Standard Study Guide
Earth’s Place in the Universe
1. Astronomy and planetary exploration reveal the solar system’s structure, scale, and change over time. As a basis for understanding this concept:
a. Know that the differences and similarities among the sun, the terrestrial planets, and the gas planets may have been established during the formation of the solar system.
· During the formation of the solar system while the sun was forming in the center of the nebular the planets where forming.
· There are two types of planets the inner(terrestrial) and the outer (gas planets)
· The terrestrial planets are rocky and have a solid surface
· The terrestrial planets from the Sun are Mercury, Venus, Earth, and Mars
· The gas planets also known as the gas giants are very large
· The gas giants are composed primarily of gassed and may not have a solid surface
· The terrestrial planets lost their original atmosphere because they did not have enough gravity to hold on to the hydrogen and helium when the sun started to fuse
· The gas planets are larger in part because they are farther from the sun so lighter elements can exist as Ice and therefore do not get blown away by the solar winds
· The asteroid belt between Mars and Jupiter contains enough material to create a planet
· The asteroid belt did not form a planet because Jupiter’s gravity was so large that whenever two rocks came together the gravity would pull them apart
b. Know that the evidence from Earth and moon rocks indicates that the solar system was formed from a nebular cloud of dust and gas approximately 4.6 billion years ago.
· Our solar system formed from a solar nebula about 4.6 to 5 billion years ago
· A nebula is a giant cloud of gas and dust composed mostly of hydrogen
· The nebula started to shrink under the force of its own gravity
· As the nebula shrank it started to spin most of the mass is in the center where at the sun
· The only material that did not end up in the sun was the material that was spinning around the sun
· The solar system is disk shaped because all of the material above and below the sun that did not spin was pulled into the sun
· The oldest rocks are 4.6 billion years old
· Rocks are dated by using radioactive dating of isotopes inside the rocks
c. Know that the evidence from geological studies of Earth and other planets suggest that the early Earth was very different from Earth today.
· Earth was originally molten when it first formed
· Earth formed when asteroids collided together
· Three things made the Earth molten: friction from meteor impacts, gravity form the material collapsing in on its self, and radioactive decay of primarily uranium, plutonium, and thorium
· When the Earth was molten the dense elements (iron and nickel) sank to the middle of the planet and the less dense material rose to the crust
· The separation of material had to occur when the Earth was molten because solids cannot flow
· The process that cause the layer of the Earth to form is differentiation
· Earth’s first atmosphere was mostly hydrogen and helium was blown away by the solar winds
· Earth got its second atmosphere from out-gassing when gasses trapped inside the planet migrated to the surface because of differences in density
· The second atmosphere did not have any free oxygen and therefore the iron that was left on the surface did not rust or oxidize
· There was no oxygen in the first atmosphere because the iron in the rocks did not oxidize or rust.
· The oxygen in the atmosphere is a direct result of photosynthesis by cyanobacteria
· When the oxygen was forming in the atmosphere some rock deposits contained bands of rusted (oxidized) iron and bands of non-rusted iron
d. Know that the evidence indicating that the planets are much closer to Earth than the stars are.
· Evidence that planets are closer to Earth than stars: planets appear to wander in the night sky, calculations using parallax determines the distance the planets are from the Earth
· Planets are smaller than stars but appear the same size because they are closer.
· As stars move away from us the color shifts to the red, and when they move closer to us their color shifts to the blue (the Doppler Effect).
e. Know that the Sun is a typical star and is powered by nuclear reactions, primarily the fusion of hydrogen to form helium.
· The sun gets its energy by a complex process called fusion where six hydrogen atoms are combined to form a helium atom and two positrons
· In large stars when the hydrogen starts to run out three helium are fused to form carbon then helium and carbon fuse to form oxygen. Elements continue to fuse until iron is produced.
· No element heavier than iron is form from the fusion inside stars
· Stars absolute magnitude and color are plotted on an HR diagram
· Our sun is considered a main sequence star based on where it plots on the H-R diagram
· Only very large stars go super nova our sun will eventually become a white dwarf
· The color or solar spectrum of thousands of stars has been studied
· The spectrum tells us what the star is composed of (each element emits a unique spectrum)
· We know that our sun is a typical star by comparing its solar spectrum to thousands of other stars
f. Know that the evidence for the dramatic effects that asteroid impacts have had in shaping the surface of planets and their moons and in mass extinctions of life on Earth.
· The Earth got its heat from three factors: meteor and asteroid collisions, compression from gravity, and radioactive decay
· Early in Earth’s history most of the heat came from meteor and asteroids collisions
· Today Earth gets most of its heat from radioactive decay
· The moons craters are evidence that there were many meteor impacts early in the formation of the solar system
· The meteor impacts on the moon are still present today because the moon does not experience erosion or plate tectonics that would destroy the craters
· Most of the craters on Earth got destroyed by erosion and plate tectonics
· The moon gets more meteor and asteroid impacts for two reasons’ there is no atmosphere to make the meteors burn up, and the Earth’s gravity deflects some objects into the moon.
· There is evidence of meteor impacts on Earth. About 65 MYA a large meteor struck Earth off of the Yucatan Peninsula causing the extinction of the dinosaurs. There an impact crater that is well pressured in Arizona
2. Earth-based and space-based astronomy reveal the structure, scale, and changes in stars, galaxies, and the universe over time. As a basis for understanding this concept:
a. Know that the solar system is located in an outer edge of the disc-shaped Milky Way galaxy, which spans 100,000 light years.
· Our solar system is in the Milky Way galaxy
· The solar system is about 2/3 from the center or 1/3 from the outer edge
· The Milky Way galaxy is about 100,000 light years across. It takes light 100,000 years to go from one edge to the next
· There are four types of galaxies irregular, elliptical, spiral, and a barred spiral
· Spiral and barred spiral galaxies are disk shaped
· The Milky Way is a spiral galaxy
b. Know that galaxies are made of Billions of stars and comprise most of the visible mass of the universe.
· The universe 15 billion years ago consisted of all matter condensed into a small area
· 15 billion years ago the was a big thermonuclear explosion called the big bang
· All matter in the universe came from the big bang
· Soon after the Big Bang there were ripples in space that consisted of concentrations of matter
· Today most of all visible matter is in galaxies
· The space between galaxies is mostly empty
· Each galaxy is composed of billions of stars
· There are billions of galaxies in the universe
c. Know that the evidence indicates that all elements with an atomic number greater than that of lithium have been formed by nuclear fusion in stars.
· Stars get there energy from fusion
· Fusion is when two or more lighter elements are combined to form heaver elements
· Fusion of hydrogen to form helium occurs in three steps
· As part of the fusion process two hydrogen protons get converted into neutrons
· Neutrons are slightly lighter than protons
· The amount of energy generated is determined by Einstein’s equation E=mc2
· After a star uses most of their hydrogen they start to fuse helium to make carbon.
· The fusion process continues until iron is produced.
· Elements heaver than iron cannot be formed from fusion in stars, only when stars go super nova.
· Immediately after the big bang hydrogen, helium, and lithium where the only elements present.
· In order for fusion to occur the atoms have to be at high temperature and moving at very high velocities
d. Know that stars differ in their life cycles and that visual, radio, and X-ray telescopes may be used to collect data that reveal those differences.
· All of the information we have about stars comes from studying its spectrum and intensity
· A stars spectrum is the amount and type of radiation that it emits
· A stars spectrum includes X-rays, gamma rays, ultraviolet light, visual light, radio waves micro-waves, and inferred radiation
· Every element when supper heated gives of a unique blend of radiation from the previous list
· By studying the radiation that a star gives off scientists can determined which elements are present
· A stars size is determined by the intensity or amount of radiation that is given off
· The intensity and color of a star is plotted on a Hertzsprung-Russell (H-R) diagram
· According to the diagram most stars plot along a band called the main sequence only very large or small stars are not considered to be main sequence stars
· Our sun is a main sequence star
· After a star fuses its hydrogen it starts to fuse helium to form other heavy elements
· When large stars use up their hydrogen they eventually go super nova (a large explosion) and can end up as a black hole
· When medium and smaller stars like our sun use up their hydrogen they become a red giant then became a white dwarf
Dynamic Earth Processes
3. Plate tectonics operating over geologic time have changed the patterns of land, sea, and mountains on Earth’s surface. As the basis for understanding this concept:
a. Know that features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics.
· Before the theory of plate tectonics there was the hypotheses of continental drift
· Continental drift states that the continents were once connected then drifted apart
· The evidence for continental drift is: the contents fit together, the same plant and animal fossils occur on multiple continents, the climate has vastly change on continents
· The evidence for plate tectonics in the same as for continental drift with additional evidence
· The first piece of evidence for plate tectonics is sea-floor spreading
· In the middle of the Atlantic ocean there is a ridge created by a chain of volcanoes
· The ocean floor is being pulled apart in the middle of the Atlantic ocean
· As the floor is pulled apart new magma from the mantle rises and creates new ocean floor
· The Earth’s magnetic field switches sometimes the magnetic north pole is north and sometimes it is in the south
· The iron in the magma aligns with the Earth’s magnetic field and is preserved when the magma cools
· As a result the rock on the ocean floor has rock with an alternating magnetic pattern
· The alternating magnetic pattern is used to discover the different ages of rocks near the mid ocean ridge
· The youngest rocks on the ocean floor are near the ridge
· The oldest ocean rocks are near deep sea trenches where the old ocean crust is being subducted and destroyed
b. Know that the principal structures that form at the three different kinds of plate boundaries.
· There are three types of plate boundaries: convergent, divergent, and strike-slip
· At convergent plate boundaries there is a shorting of the curst
· There are three types of convergent plate boundaries: ocean-ocean, continental-continental, and ocean-continental
· Ocean-Ocean one ocean plate goes under the other a deep sea trench is formed and an island arc like Japan
· Continental-continental there is an uplifting of the crust resulting in very high mountains like the Himalayan mountains
· Ocean-continental a deep sea trench forms and a volcanic arc like the cascade range in northern California, Oregon, and Washington
· A divergent plate boundary is where there is a lengthening of the earth’s crust if the boundary is under water a mid ocean ridge forms if on land a deep canyon forms.