Earth 101 | National Geographic

How did Earth initially form?

• From a giant explosion in space.

• From particles left over after the Sun was created.

• From a collision between two large planets.

• From a massive cloud of ice and gas.

Which of the following is the correct order of Earth's layers from the center outwards?

• Liquid outer core, solid inner core, silicate mantle, rocky crust.

• Solid inner core, liquid outer core, silicate mantle, rocky crust.

• Rocky crust, silicate mantle, liquid outer core, solid inner core.

• Silicate mantle, rocky crust, solid inner core, liquid outer core.

What is a key reason Earth can have liquid water, unlike Mercury or the gas giants?

• Earth has a strong magnetic field.

• Earth is the third planet from the Sun, at an ideal distance.

• Earth has a large moon that stabilizes its orbit.

• Earth's atmosphere is very thick.

What were the earliest known lifeforms on Earth?

• Dinosaurs

• Fish

• Microbial organisms

• Plants