1. Rocks are constantly changing: This is known as the rock cycle. Rocks can be broken down into smaller pieces by weathering, then carried away and deposited as sediment. This sediment can be compressed and cemented together to form new sedimentary rocks. Heat and pressure can transform sedimentary or igneous rocks into metamorphic rocks. And finally, molten rock (magma) can cool and solidify to create igneous rocks.

2. Rocks can tell us about Earth's history: By studying the composition, texture, and age of rocks, geologists can learn about past climates, environments, and even the age of our planet. Fossils found in sedimentary rocks provide clues about the history of life on Earth.

3. Not all rocks are solid: Some rocks, like pumice, are actually very porous and can float on water. This is because they contain trapped gas bubbles from the volcanic eruptions that created them.