| A | B |
|---|
| What caused the Earth to heat up soon after its formation? | meteorite impacts, weight of overlying material, decay of radioactive materials |
| How long ago did the Earth form? | 4.6 billion years ago |
| How long does it take for the Earth to make one complete turn on its axis? | 24 hours |
| What does the Earth's revolution and tilt cause? | seasonal changes |
| What is the longest day of the year? | summer solstice |
| What is the shortest day of the year? | winter solstice |
| On what occasions are day and night of equal lengths? | vernal & autumnal equinoxes |
| How does the nebular hypothesis suggest that the Earth was formed? | whirling cloud of gas and debis into multilayered sphere |
| How was the sun formed? | fusion of the gas cloud material |
| What did planetesimals eventually develop into? | planets & moons |
| What did the 3rd closest planet become? | Earth |
| What did the spinning of the young Earth cause? | form a sphere that bulges in the center |
| What is the shape of the Earth called? | oblate sphere |
| What percentage of the Earth is covered by water? | 71% |
| What percentage of the Earth's surface is dry land? | 29% |
| What is the total surface area of the Earth? | 510 million square km |
| What are the layers of the Earth? | inner core, outer core, mantle, crust |
| What composes the Earth's center or innercore? | solid iron and nickel |
| What composes the Earth's outer core? | liquid iron and nickel |
| What composes the Earth's mantle? | iron, silicon, magnesium |
| What composes the Earth's crust? | thin, rigid layer of lighter rocks |
| What is the thickest of the Earth's layers? | mantle |
| What is the crust and uppermost portion of the mantle together make? | lithosphere |
| What is the smallest of the Earth's layers? | crust |
| What in magnetic north pole equivalent to? | positive end of a bar magnet |
| What is the magnetic south pole equivalent to? | negative end of a bar magnet |
