Formation of Earth (review)

In general, planets that have a greater number of craters on their surface are:

• younger.
• bigger.
• older.
• more dense.

Terrestrial planets are usually:

• closer to their star than gas giants.
• less dense than ice giants.
• larger than gas giants.
• older than ice giants.

One major difference between the Earth and the Moon is:

• the Earth does not have an atmosphere.
• The Earth is much smaller than the Moon.
• The Moon is much older than the Earth.
• The Moon does not have plate tectonics.

As you move further away from the center of the solar system:

• the planets get smaller.
• the planets get less dense.
• the planets get warmer.
• all of the above.

Which of the following lists the types of planets in the correct order from least dense to most dense?

• terrestrial, gas giant, ice giant
• ice giant, terrestrial, gas giant
• gas giant, ice giant, terrestrial
• gas giant, terrestrial, ice giant

Scientists are able to determine how the Earth formed by:

• radioactive dating of meteorites.
• analyzing craters on the Earth and Moon.
• studying the size an composition of other planets.
• all of the above.

Earth does not have nearly as many craters as the Moon because:

• the Moon protected the Earth from many asteroid impacts.
• the Earth's magnetic field deflects incoming asteroids.
• many of the Earth's craters have eroded away.
• the Earth isn't as old as the Moon.

The amount of time it takes for 50% of a sample of a radioactive element to decay is called its:

• decay rate.
• half-life.
• half-blood.
• lifespan.

Gas giants are:

• almost always larger than terrestrial planets.
• usually habitable.
• much more dense than ice giants.
• all of the above.

When an unstable element like uranium turns into a more stable element like thorium, it is called:

• plate tectonics.
• erosion.
• a supernova.
• radioactive decay.