Mrs. Davis’

8th Grade Science

Objective 5: Earth and Space Systems

Universe: space and the matter and energy it contains

Galaxy: system (large group) of stars in space; there are 3 types of galaxies as shown below

Star: huge, hot body made of different gases; radiates energy; a star’s temperature is related to the color of light the star gives off; a star’s brightness depends on its temperature, size, and distance from Earth

Planets: objects that revolve around a star; in our solar system the planets that revolve around our Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune

Sun: star that is the center of our solar system; provides most of Earth’s energy

Moon: object that revolves around a planet; a natural satellite

Phases: stages that the moon goes through when it revolves around the Earth each month

Seasons: natural divisions of the year caused by the tilt of the Earth’s axis, combined with its revolution around the Sun

Equinox: the two times per year when the Sun is directly over the equator; length of day and night are the same; in the northern hemisphere it occurs in March and is known as the Vernal or Spring Equinox and in September and is known as the Autumnal or Fall Equinox

Solstice: the two times per year when the Sun is farthest from the equator; in the northern hemisphere the Summer Solstice occurs in June and is the longest day of the year, and the Winter Solstice occurs in December and is the shortest day of the year.

Tides: the daily movement (rise and fall of the Earth’s ocean surfaces; caused by the moon’s pull of gravity on the Earth

Lunar Eclipse: moon moves into the Earth’s shadow

Solar Eclipse: moon’s shadow crosses Earth

Earth revolves around the Sun once a year (365 ¼ days)

Moon revolves around the Earth once a month (29 ½ days)

Earth rotates on its axis once a day (24 hours)

Changes: different events cause the Earth’s surface and animal populations to change over time; can be cause by catastrophic natural events (Ex. earthquakes or volcanoes erupting) or by humans (Ex. pollution, unregulated hunting, new species introduction)

Erosion: moving rocks or soil from one place to another due to water, wind, or gravity

Weathering: breaking down of materials like rocks into smaller pieces (Ex. soil, sand, or dirt)

Deposition: dropping eroded rock and soil to new locations

Natural Resources: a substance that helps support life on Earth

Resource Type                 Time to Replace             Example

Renewable            within a person’s lifetime trees, oxygen

Nonrenewable                   millions of years            oil, gas, coal

Inexhaustible        not used up                                  sun, wind, tides

Fossil Fuels: energy sources (coal, oil, and gas) that were made over many years from the remains of living things

Negative Human Impact – Ex. air, water, and soil pollution, deforestation

Positive Human Impact – Ex. conservation, habitat preservation, recycling

Plate Tectonics: theory that the lithosphere (earth’s outermost layer) is divided into plates that slowly but constantly move

Boundary        Plate Movement        Possible Results

Convergent       collide àß                   mountain, volcano

Divergent         move away ß à       rift valley, earthquakes

Transform        slide past                   fault lines

Continental Drift: theory that the continents may have once been connected and have been moving away from each other ever since

Land Subsidence: sinking of areas of the Earth’s crust; caused by underground voids or compaction

Igneous Rock: hot magma cools and hardens

Sedimentary Rock: rock pieces deposited and compacted together

Metamorphic: existing rock changes due to heat and pressure

The Rock Cycle

Magma: liquid rock inside the Earth’s crust

Lava: term for magma on the Earth’s surface

Water Cycle: constant movement of water between the Earth’s surface and air; goes back and forth between liquid and vapor

Transpiration: water vapor released into the atmosphere by plants

Evaporation: liquid to vapor

Condensation: vapor to liquid

Precipitation: water that falls to Earth (Ex. rain, snow, sleet, or hail)

Watershed: land area which drains surface water into a body of water like a stream

Surface Water: water on Earth’s surface (Ex. Lakes, streams, and oceans)

Ground Water: water beneath land surface and is trapped in porous rocks or soil; provides water to plants, wells, and springs