Vocabulary#12 Moving Plates

Crust:Earth`s solid,rocky surface containing the continents and ocean floor.
S:For example when an earthquake occur the crust is moving.

Original horizontality:The idea that many kinds of rocks from in flat,horizontal layers.
S:The layers of sedimentary rock were once original horizontality.

Continental drift:The idea that a supercontinent split apart into pieces,the continents,which drifted in time to their present locations.
S:Pangaea was a supercontinent were there occur the continental drift.

Sea-floor spreading:The idea that new crust is forming at ridges in the sea floor,spreading apart the crust on either side of the ridges.
S:Scientist suggested a model to explain the huge crack called sea-floor spreading.

Magma:hot ,molten rock below Earth`s surface.
S:Magma flows through cracks,cools and hardens into new solid rock along the ridges.

Plate Tectonics:The idea that Earth`s surface is broken into plates that move.
S:Earth`s surface is broken in plates.

Mantle:Earth`s layers beneath the crust.
S:Plates move aroun in low portion of mantle.

Subduction:Where plates collide,the sliding of a denser ocean plate under another plate.
S:Subduction is a part of a cycle.

Vocabulary#11 Galaxies and Beyond

Galaxy:A large group of stars held together by gravity.
S:The stars orbit the center of their galaxy.

Milky Way:Our home galaxy.
S:We live in the Milky Way.

Spectrum:A band of colors made when white light is broken up.
S:The light produce spectrum.

Expansion Redshift:The shift of spectrum of a galaxy toward longer(redder)Wavelenght due to the expansion of space.
S:It is called redshift because the light`s spectrum has been shifted to longer Wavelenght.

Big Bang:The beginning of the universe,when the density of the universe was very high.
S:The universe has expanded ever since Big Bang.

Background Radiation:Electromagnetic radiationleft over from the Big Bang.
S:The Background radiation was discovered in the 1960s.

Quasar:An extremely bright,extremely distant,high-energy source.
S:Quasar must be very,very old.

Vocabulary#10 Stars

Star:A large ,hot ball of gases, which is held together by gravity and gives off its own light.
S:Stars are far,far away from Earth.

Parallax:The apparent shift in an object`s location when viewed from two positions.
S:The closer a star is,t he greater the shift of a parallax is.
 
Light-Year:The distance light travels in a year.
S:Astronomers use a unit called light-year(ly).

Constellation:A number of star that appears to form a pattern.
S:My favorite constellation is the Lyra.

Magnitude:The brightness of a star.
S:The Magnitude is use in two ways in absolute and apparent magnitude.

Nebula:A cloud of gas and dust in space.
S:As time goes,the gravity cause nebula to contract.

Supernova:A star that explodes.
S:When a star collide or explode is called supernova.

Black hole:An object whose gravity is so strong that light cannot escape it.
S:When a star collapse it becomes a black hole.

Vocabulary#9 The Outer Solar System

Comet:a ball of rock and ice that orbits the Sun.
S:Comets come from the outer fringes of the solar system.

Meteoroid:A small asteroid(rocky object that obit the Sun)which may be far out in the solar system or close to the Inner Planets.
S:Sometimes the meteroid collide with the atmosphere of a planet,such as Earth.

Meteor:A meteroid that enters Earth`s atmosphere and burns with a streak of light.
S:Sometimes a meteor burns completely.

Meteorite:Any part of a meteoroid that reaches Earth`s surface.
S:Meteorites are usually classified in three types.