8Th Grade Science Essentials

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1st Quarter

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The moon phase halfway between new moon and full moon, when half of the side facing Earth is lighted.

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3rd or last quarter

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The moon phase halfway between full, moon and new moon, when half of the side facing Earth is lighted.

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Absolute Dating

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Any method of measuring the age of an event or object in years.

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Air Mass

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A large body of air that has the same properties as the surface over which it formed

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Air Pressure

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The measure of the force with which air molecules push on a surface

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Air Pressure

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The measure of the force with which air molecules push on a surface

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Asthenosphere

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The plastic-like layer below the lithosphere in Earth’s mantle.

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Astronomical Unit

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The average distance from Earth to the sun (150 million km), used for measuring distances to objects in the solar system.

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Axis

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Imaginary line that runs through the Earth vertically.

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Cementation

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A sedimentary rock-forming process in which large sediments are glued together by minerals deposited between the sediments.

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Cinder Cone

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A type of volcano in which tephra piles up into a steep-sided cone

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Cirrus

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Thin, feathery, white clouds found at high altitudes. Form if the wind is strong.

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Cleavage

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The physical property of a mineral that causes it to break along smooth, flat surfaces.

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Climate

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The average weather conditions in an area over a long period of time.

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Clouds

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A collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs.

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Cold front

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the boundary that develops when a cold air mass pushes under a warm air mass.

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Compaction

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A sedimentary rock-forming process that occurs when layers of small sediments become compressed by the weight of layers above them.

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Composite Volcano

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A type of volcano built of silica-rich lava and tephra layers accumulated from repeated alternating cycles of tephra eruptions and lava eruptions.

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Compression

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Squeezing forces that compress rocks together at convergent plate boundaries, causing them to deform, fold, and sometimes break.

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Condensation

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The change of state from a gas to a liquid. When water vapor cools and changes into water droplets that form clouds in the atmosphere.

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Conduction

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The transfer of heat that occurs when molecules collide

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Constellation

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A grouping of stars that has a shape resembling an animal, mythological character, or other familiar object and thus is named for it.

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Continental Drift

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A hypothesis proposed by Alfred Wegener, which states that continents have moved horizontally around the globe, over time, to reach their current locations

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Convection current

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The driving force of plate tectonics in which hot, plastic-like material from the mantle rises to the lithosphere, moves horizontally, cools and sinks back to the mantle.

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Convection

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The transfer of heat by a flow of a heated material; occurs in gases or liquids.

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Convergent Boundary

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In plate tectonics, the boundary between two plates that are converging, or moving toward each other.

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Core

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The central part of the Earth below the mantle.

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Crust

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The outermost layer of Earth, varying in thickness from more than 60 km to less than 5 km.

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Crystal

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A solid having a distinctive shape because its atoms are arranged in repeating patterns.

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Cumulus

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Puffy, white clouds that tend to have flat bottoms. Form when warm air rises.

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Deformation

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The bending, tilting, and breaking of the Earth’s crust; the change in the shape of rock in response to stress.

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Deposition

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The final step in an erosional process, in which sediments are dropped by running water, wind, gravity or glaciers as their energy of motion decreases

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Dew Point

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The temperature at which air is saturated with water and condensation begins.

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Divergent Boundary

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In plate tectonics, the boundary between two plates that are diverging, or moving away from each other.

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Earthquake

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The movement of the ground, caused by waves from energy released as rocks move along faults.

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Ellipse

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An elongated, closed curve; the shape of Earth’s orbit.

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Epicenter

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The point on Earth’s surface directly above an earthquake’s focus.

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Equinox

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The two times each year that the sun is directly above Earth’s equator and the day and night are of equal length all over the world; the start of spring and fall.

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Erosion

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The process that wears away surface materials and moves them from one location to another, usually by gravity, glaciers, wind or water.

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Evaporation

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When water from the oceans and the Earth’s surface changes into water vapor. The change of state from a liquid to a gas.

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Exosphere

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Uppermost part of the Earth’s atmosphere. Beyond it lies space.

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Extrusive

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Igneous rocks that form when magma extrudes onto Earth’s surface and cools as lava; have a fine-grained texture.

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Fault

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Surfaces along which rocks break and move; rocks on either side of a fault move in different directions relative to the fault surface.

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Focus

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The point in Earth’s interior where earthquake energy is released.

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Folding

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The bending of rock layers due to stress.

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Foliated

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A type of metamorphic rock created when mineral grains flatten and line up in parallel bands.

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Fossil

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The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock.

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Fracture

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The physical property of a mineral that causes it to break with rough or jagged edges.

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Front

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in weather systems, the boundary between two air masses.

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Full Moon

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The moon phase when the side facing Earth is completely lighted because Earth is between the sun and the moon.

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Galaxy

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: A massive grouping of stars, gas and dust in space, held together by gravity; can be elliptical, spiral or irregular.

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Greenhouse effect

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Natural heating caused by atmospheric gases trapping heat at Earth’s surface.

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Hardness

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A measure of how easily a mineral can be scratched.

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Hot Spot

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Areas in Earth’s mantle that are hotter than the neighboring areas, forming melted rock that rises toward the crust.

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Humidity

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The amount of water vapor held in the air.

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Hurricane

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A severe storm that develops over tropical oceans and whose strong winds of more than 120 km/h spiral in toward the intensely low-pressure storm center.

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Igneous Rock

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Rock formed by the cooling and hardening of molten material from a volcano or from deep inside Earth.

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Inner Core

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The dense, solid center of Earth, formed mostly of iron & nickel.

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Inner/Terrestrial Planets

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The four solid, rocky planets closest to the sun – Mercury, Venus, Earth, and Mars.

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Intrusive

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Igneous rocks formed when magma cools below Earth’s surface; generally have large mineral grains.

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Ionosphere

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Area of the Thermosphere with electrically charged particles, called ions. This is where auroras and radio signals bounce back to Earth

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Lava

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Molten rock from a volcano flowing onto Earth’s surface.

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Light Year

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A unit used to measure distance in space; the distance that light travels in one year.

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Lightning

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An electric discharge that takes place in between two oppositely charged surfaces, such as between a cloud and the ground, between two clouds, or between two parts of the same cloud.

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Lithosphere

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The rigid, outermost layer of Earth, about 100km thick, composed of the crust and part of the mantle.

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Lunar Eclipse

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An eclipse that occurs when Earth passes between the sun and moon, and Earth’s shadow falls on the moon, preventing sunlight from reaching all or part of the moon.

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Luster

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The physical property of a mineral that describes how light is reflected from its surface; is defined as either metallic or nonmetallic

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Magma Chamber

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The body of molten rock that feeds a volcano.

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Magma

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Hot, melted rock material beneath Earth’s surface.

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Magnitude

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: In earthquake studies, a measure of the energy released by an earthquake; the Richter scale is used to describe earthquake magnitude.

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Mantle

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the thickest layer inside Earth; it lies between the outer core and the crust and is described as plastic-like; formed mostly of silicon, oxygen, magnesium and iron.

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Mesosphere

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The strong lower part of the mantle between the asthenosphere and the outer core. Also, the layer of the atmosphere between the stratosphere and the thermosphere and in which temperature decreases as altitude increases.

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Metamorphic Rock

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Rock formed from sedimentary, igneous, or other metamorphic rock due to increases in heat or pressure.

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Meteor

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A meteoroid that enters Earth’s atmosphere and burns up as it falls; also called a shooting star.

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Meteorologist

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A scientist who studies weather conditions using radar, satellites, and other instruments to make weather maps and forecasts.

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Mineral

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a naturally occurring, inorganic solid with a distinct internal structure and chemical composition.

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Moon Phase

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The change in appearance of the moon as it orbits Earth every 29 ½ days, depending n the relative positions of the moon, Earth, and the sun; for example, full moon and new moon.

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Nebula

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A large cloud of gas and dust in space that may be the beginning of a star.

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New Moon

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: The moon phase when the side facing Earth is completely dark and cannot be seen because the moon is between Earth and the sun.

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Nonfoliated

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A type of metamorphic rock created when mineral grains change, grow, and rearrange, but don’t form bands.

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Nuclear Fusion

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The combination of the nuclei of small atoms to form a larger nucleus; the binding energy of the atomic nucleus.

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Occluded front

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In weather systems, the boundary that results when two cool air masses merge and force warmer air to rise between them.

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Orbit

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The curved path followed by a satellite as it travels around a star, planet, or other object.

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Outer Core

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The liquid layer of Earth’s core that surrounds the solid inner core and is comprised of iron and nickel.

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Outer/Gaseous Planets

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The five planets farthest from the sun – Jupiter, Saturn, Uranus, Neptune, and Pluto.

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Paleontology

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The scientific study of fossils.

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Pangaea

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The name Alfred Wegener gave to the large landmass, made up of all continents, that he believed existed before it broke apart to form the present continents.

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Parallax

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The apparent shift in position of an object when viewed from two different points, such as your left eye and right eye.

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Percolation

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The downward movement of water through pores and other spaces in soil due to gravity.

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Plate Tectonics

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The theory that Earth’s crust and upper mantle (lithosphere) are broken into sections, called plates, that slowly move around on the mantle.

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Plate

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In plate tectonics, a section of Earth’s lithosphere (crust and upper mantle) that moves around on the mantle.

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Precipitation

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Rain, snow, sleet, or hail that falls from clouds onto the Earth’s land and oceans.

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Primary Wave

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Waves of energy, released during an earthquake, that travel through Earth by causing particles in rocks to compress and stretch apart in the direction of the wave.

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Prograde

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Counterclockwise spin of a planet or moon as seen from above the planet’s North Pole; rotation in the same direction as the sun’s rotation.

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Radiation

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The transfer of energy through matter or space by electromagnetic waves.

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Recycling

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The process of recovering valuable or useful materials from waste or scrap; the process of reusing some items.

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Relative Dating

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Any method of determining whether an event or object is older or younger than other events or objects.

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Retrograde

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Clockwise spin of a planet or moon as seen from above the planet’s North Pole.

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Revolution

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The orbiting of one object around another, like Earth’s yearly orbit around the sun.

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Rift Zone

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An area of deep cracks that forms between two tectonic plates that are pulling away from each other.

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Rock Cycle

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The processes by which, over many years Earth materials form and change back and forth among igneous rocks, sedimentary rocks, and metamorphic rocks.

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Rock

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Earth material made of a mixture of one or more minerals, glass, mineraloids, or organic matter.

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Rotation

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The spinning of an object around its axis; causes day and night to occur on Earth.

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Run off

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Precipitation that flows over land into streams and rivers.

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Satellite

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: any object that revolves around another object; planets and human-made satellites are examples.

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Seafloor Spreading

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The theory that magma from Earth’s mantle rises to the surface at mid-ocean ridges and cools to form new seafloor, which new magma slowly pushes away from the ridge.

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Secondary Wave

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Waves of energy, released during an earthquake, that travel through Earth by causing particles in rocks to move at right angles to the direction of the wave.

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Sediment

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Loose materials such as rock fragments, mineral grains, and bits of plants and animals that have been transported by wind, water or glaciers.

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Sedimentary Rock

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Rock formed when fragments of rocks, minerals, and/or organic matter are compacted or cemented together or precipitate out of a solution.

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Seismic Wave

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In an earthquake, the energy waves that move outward from the earthquake focus and make the ground quake.

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Seismograph

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An instrument used by seismologist to record primary, secondary, and surface waves from earthquakes.

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Seismologist

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A scientist who studies earthquakes and seismic waves.

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Shield Volcano

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A broad volcano with gently sloping sides, built by quiet eruptions of fluid basaltic lava, which spreads out in flat layers; example: the Hawaiian Islands.

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Solar Eclipse

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An eclipse that occurs when the moon passes directly between Earth and the sun, so that the moon casts a shadow on part of Earth and blocks sunlight from reaching Earth.

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Solar System

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The system of 9 planets and many other objects that orbit our sun; may have been formed about 5 billion years ago from a cloud of ice, gas and dust.

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Solstice

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The two times each year that Earth’s tilt makes the sun reach its greatest angle north or south of the equator, marking the start of summer or winter.

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Stationary front

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In weather systems, a warm front or cold front that has stopped moving.

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Strata

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Layers of rock.

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Stratification

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Process in which sedimentary rocks are arranged in layers.

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Stratosphere

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The layer of the atmosphere that is above the troposphere and in which temperature increase as altitude increases.

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Stratus

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: Clouds that form in layers. Cover large areas of the sky and often block out the sun.

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Streak

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The color of a mineral when it is powered; usually observed by rubbing the mineral on a ceramic streak plate.

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Subduction Zone

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In plate tectonics, the area where an ocean-floor plate collides with a continental plate, and the denser ocean plate sinks under the less dense continental plate.

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Superposition

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A principle that states that younger rocks lie above older rocks if the layers have not been disturbed.

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Surface Wave

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Waves of energy, released during an earthquake, that reach Earth’s surface and travel outward from the epicenter in all directions; travel through Earth by giving rock particles an elliptical and side-to-side motion.

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Tension

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Stretching forces that can be strong enough to pull rocks apart at divergent plate boundaries.

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Tephra/ Pyroclasic Material

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Lava that is blasted into the air by violent volcanic eruptions and solidifies as it falls to the ground as ash, cinders, and volcanic bombs.

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Thermosphere

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The uppermost layer of the atmosphere, in which temperature increases as altitude increases.

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Thunder

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The sound caused by the rapid expansion of air along an electrical strike.

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Tornado

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A destructive, rotating column of air that has very high wind speeds, is visible as a funnel-shaped cloud, and touches the ground.

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Transform Boundary

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In plate tectonics, a boundary between two plates that are sliding horizontally past one another.

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Troposphere

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The layer of Earth’s atmosphere closest to the ground; contains clouds, smog, weather, and 75 percent of atmospheric gases.

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Tsunami

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An ocean wave that begins over an earthquake focus and can reach 30m high.

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Vent

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: In volcanic regions, an opening in Earth’s surface through which can flow lava, ash, cinders, smoke and steam.

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Volcano

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A vent in Earth’s surface that often forms a mountain built of lava and volcanic ash, which erupts and builds up.

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Waning

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Describes the moon following a full moon, as its visible lighted area grows smaller during the lunar cycle.

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Warm front

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The moving boundary that develops when a warm air mass meets a cold air mass.

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Water Cycle

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Te continuous movement of water from the ocean to the atmosphere to the land and back to the ocean.

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Waxing

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Describes the moon shortly after a new moon, as its visible lighted area grows larger during the lunar cycle.

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Weather

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The behavior of the atmosphere – wind, temperature, pressure, precipitation – at a particular place and time.

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Weathering

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The breaking of rocks into smaller pieces, either mechanically or chemically.