Simple machines can be evaluated by comparing measurements of force. Simple machines can be combined in different ways to create new complex machines. Simple machines are used in many tasks and occupations. Rocks can be classified as metamorphic, sedimentary or igneous. Metamorphic rocks are formed in the earth's crust by pressure and heat.
Sedimentary rocks form when sediment settles under water and becomes compacted.
Igneous rocks are created when molten rock cools and hardens. Rocks can undergo physical and chemical changes. Fossils can be found in sedimentary rock and provide evidence about plants and animals that lived long ago and the nature of the environment at that time. Places in the world often have specific types of rocks and minerals that are common to those areas. Glaciation has had a profound impact on Wisconsin rock formations.