What are strata?

What happens to radioactive elements when they decay?

What are the largest divisions of geologic time?

What is the term for a cloud of dust & gas where stars are born?

About how old to scientists think the Earth is?

In a sequence of layers, where are the oldest ones?

If you have 10 grams of carbon-14, how much will still be radioactive after 1 half-life?

During which eon did the following occur: formation of the Moon, Earth stratifying, and Earth’s crust forming?

Nuclear fusion caused what object to be born at the center of our solar system?

What is 1 place Earth's water may have come from?

What is newer, a sedimentary layer, or an intrusion that cuts through it?

If you have 19.3 grams of a radioactive substance, what will be the ratio of inert material to radioactive material after 2 half-lives?

What separates the Phanerozoic Eon from the previous eons?

Accretion caused the planets to form. What is accretion?

On your timelines, about how far from the "now" line does human history start?

What do you call a fossil that lets you identify the age of a rock layer?

If there is 16 grams of radioactive material in a sample, how long will it take until only 1 gram is still radioactive?

During the Proterozoic Eon, why did the Earth’s atmosphere begin to fill with oxygen?

Most of the iron in the Earth ended up in the core. Why?

About how long ago did the first hominids show up?

What is the term for a widespread, easily recognizable rock layer that allows matching formations in distant locations?

If a fossil has a 7:1 ratio of nitrogen-14 to carbon-14, how many years old is it? (1 half-life of C-14 is 5,730 years.)

What separates the eras of the eras of the Phanerozoic eon?

Earth's gravity swept up a lot of debris early in its history. What is this period of time called, when all this stuff was pummeling Earth?

Earth's iron core generates our magnetic field. Why is our magnetic field important?