Geology Review

Our planets surface is always changing  Tectonic plates are always growing, moving and being destroyed because of convection.  Convection is movement of material because of temperature and density differences.  The core heats the mantle, the mantle creates new plate and pushes the plates, the cooled mantel drops to the core to and repeats the process.

Fossils tell us about the planet’s history  The fossil record tells us about the planet and the type of life it could support.  The fossils describe what type of environment (underwater or above sea level), atmosphere, and whether live was possible at the time of different period on our planet.  Fossils provide evidence of the continents at one time being connected and support the continuous movement of tectonic plates.

We can use isotopes to date the planet  Radioactive isotopes help us to date rocks and fossils.  Radioactive isotopes are atoms that have different amounts of neutrons that make them unstable. Unstable atoms will decay to more stable forms by letting off protons and neutrons.  Examples are carbon-14 used to determine the age of once living materials, and uranium-238 to determine the age of rocks.  The time it takes half of a sample to decay to the more stable element is called a half live.

Earthquakes happen because of plate movement.  Earthquakes are created by movements at boundaries called faults.  Faults can be found at convergent, divergent and transform boundaries.  Earthquakes help us understand where boundaries are and what type of boundaries they are.  Tsunamis are created by earthquakes.  Earthquakes have different types of waves, P-waves and S-waves, that help use determine where the epicenter is and what our earths layers are made of.