Three Rocks in a Shoebox: reading passage and questions

On her birthday, Zadie got a shoebox from Grandpa. Inside were three rocks.

"Each one began in a different way," said Grandpa. "Want to find out how?"

The first rock was light and full of tiny holes. Zadie dropped it in a bowl of water. It floated!

"That is pumice," said Grandpa. "It is a rock that began as fire."

Deep in the Earth, rock gets so hot it melts. A volcano pushes the melted rock out. It is called lava.

Lava cools and gets hard. Bubbles in it get stuck inside. They are the holes in the pumice.

The second rock was tan, with stripes. Zadie ran her finger along them. Each stripe was a layer of sand.

Long ago, sand settled in a lake, layer on layer. More layers piled up. Their weight packed the sand down hard.

After a very long time, the sand turned to stone. Zadie could still see the layers.

The third rock was dark gray and flat. Zadie tapped it, and a thin sheet came off.

"That is slate," said Grandpa. "It began as soft black mud under a sea."

Heat and squeezing made the mud hard and flat. It did not melt. It looks like a roof tile.

Zadie and Grandpa took the rocks to the creek. Zadie rubbed the tan rock on a big flat stone. Sand came off on her fingers.

"The creek does this," said Grandpa, "just slower." The sand drifts down the creek and settles. One day it may be packed into stone again.

Sand can become stone, and stone can become sand again. That ride is the rock cycle. It takes longer than anyone has been alive.

Zadie set her three rocks in a row. One began as fire, one as sand, one as mud.

Zadie smiled at the rocks in a row. Which one would you pick up first?