1. Why do we believe the Earth has an iron core?
A Samples from deep holes are iron rich.
BX-ray cameras show a dark, impenetrable mass at the planet's center.
C The properties of seismic waves match those expected of a region of iron.
DAstronomers have seen asteroid impacts sinking into the deep interior.
EVolcanoes erupt nearly pure iron.Astronomers have seen asteroid impacts sinking into the deep interior.
2. What might explain how the core formed?
AAsteroids hitting and penetrating.
BIron sinking to the core as the bulk of the Earth melted.
CThe magnetic field pulling it inward.
DEarthquakes shake the planet and the iron gradually "sifts" downward.
EThe silicon of the crust decays into iron at high temperatures.
3. Why is the core hot?
AFrom the steady decay of radioactive atoms in the rock.
BFrom heat left over from the planet's birth.
CFrom sunlight leaking into the interior over millions of years.
DAll of the above
EOnly A and B
4. What causes auroras?
ASunlight reflected off meteor dust high in the atmosphere.
B Micro-meteorites burning up as they sweep along the Earth's magnetic field.
C Particles from the Sun colliding with and exciting atoms in our upper atmosphere.
D Fluorescence by upper atmospheric hydrogen atoms.
E Waves in the magnetic field creating an upper atmospheric laser-like effect.
5. What causes the greenhouse effect ?
A Water vapor and carbon dioxide absorb visible sunlight and warms the atmosphere.
BOzone absorbs solar ultraviolet radiation and warms the atmosphere.
C Oxygen and nitrogen scatter sunlight which heats the atmosphere by its frictional passage.
D Water vapor and carbon dioxide absorb infrared radiation from the ground and reradiate the heat toward the surface.
E Flurocarbons absorb infrared radiation from the Sun and heat the surface.