• Formed from sediments (rock fragments, mineral grains, animal & plant remains) that are pressed or cemented together or when sediments precipitate out of a solution.
• These sediments are moved by wind, water, ice or gravity.• Sedimentary rocks represent 7% of the Earth’s crust, but they cover 70% of the Earth’s surface.• Sedimentary rocks are fossil-carrying rocks.
What turns sediments into solid rock?1)Water or wind breaks down anddeposits sediment (erosion & deposition)
2)The heavy sediments press down onthe layers beneath (compaction)
3)Dissolved minerals flow between theparticles and cement them together(cementation)
How can sedimentary layers help us understand the age of fossils?• As sedimentary rocks are deposited, they form horizontal layers• Scientists know that the layers on top (and the fossils in the top layer) are YOUNGER than the fossils in lower layers.
• Rocks that have changed due to intense temperature and pressure• “Meta” means “change” and morphosis means “form” in Greek• Igneous, sedimentary and other metamorphic rocks can change to become metamorphic rocks
What occurs in the Earth to change these rocks? • Pressure from overlying rock layers • High heat, but not enough to melt the rock • Rocks may be flattened or bent or atoms may be exchanged to form new minerals.
• *You can think of metamorphic rocks as a squished peanut butter & jelly sandwich in your lunch.
QUESTIONS1. What are the three types of rocks?2. What type of rocks hold fossils?3. What are the 2 kinds of igneous rocks?4. What kind of igneous rocks are formed below the earth’s surface?5. What kind of rock has the Grand Canyon formed in?6. What are rocks made of?7. Will an igneous rock stay an igneous rock forever?