VOCABULARY Nº15

Fold mountain: a moountain made mostly of rock layers.








Fault-block mountain: a mountain made by huge titled.





Weathering: the breaking down of rock.





Erosion: the picking up.





Soil: a mixture of weathered rock.





Soil horizont: any of the layers of soil.





Groundwater: water that soaks into soil and rock.





Humus: material in soil.

VOCABULARY Nº14

Hot spot: a very hot part of the mantle, where magma can melt through a plate moving above it.





Vent: a central opening in a volcanic area through which magma may escape.









Lava: magma that reaches Earth's surface and flows out of a vent.







Crater: a cuplike hollow that forms at the top of a volcano around the vent.








Cinder-cone volcano: a steep-sided cone that forms from explosive eruptions of hot rocks, ranging from particles to boulders.








Shield volcano: a wide, gently sloped cone that form from flows of lava.








Composite volcano: a cone formed from explosive eruptions of hot rocks followed by a flow of lava, over and over.








Geothermal energy: heat from below Earth's surface.

VOCABULARY Nº13

Fault: a huge crack in the crust, at or below the surface, the sides of which may show evidence of motion.





Focus: the point where an earth-quake starts, where rocks begin to slide past each other.





Seismic wave: a vibration that spreads out away from a focus when and earthquake happens.





Epicenter: the point on Earth's surface directly above the focus.





Seismograph: a sensitive device that detects the shaking of the crust.








Magnitude: the amount of energy released by an earthquake.

VOCABULARY Nº12

Crust: Earth's solid, rocky surface containing the continents and oceans floor.








Original horizontality: the idea that many kinds of rocks form in flat, horizontal layers.








Continental drift: the idea that a supercontinent split apart into pieces, the continents, which drifted in time to their present locations.





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.





Magma: hot, molten rock below Earth's surface.








Plate tectonics: the idea that Earth's surface is broken into plates that move.





Mantle: Earth's layer beneath the crust.








Subduction: where plates collide, the sliding of a denser ocean plate  under another plate.

VOCABULARY Nº11

Galaxy: a large group of stars held together by gravity.








Milky way: our home galaxy.





Spectrum: a band of color made when white light is broken up.








Expansion redshift: the shift of a spectrum of a galaxy toward longer (redder) wavelenghts due to the expansion of space.








Big band: the beginning of the universe, when the density of the universe was very high.








Background radiation: electromagnetic radiation left over from the big band.








Quasar: an extremely bright, extremely distant, high-energy source.