Paleontologists' Tool Kit

Scientists understand ancient life by making observations, and interpreting them based on all available information.

We assert that fundamental physics have remained the same through time.


 * We frequently say, "the present is the key to the past" - that today's environments and habitats teach us about past rocks and life.
 * We also see habitats and environments in Earth's past that have no matching example today. Earth and its life have changed so radically through time that we can't expect an example of every single thing to be here at one time.

Paleontologists must consider:


 * How fossils form - chemistry & physics that change a dead animal into an enduring stone record
 * How different habitats create sedimentary rocks
 * How habitats have changed through time and space
 * Where fossil-rich rocks will be accessible on Earth's surface today

The Earth's Crusty Bits
The Earth's surface wears a crust of rocks, minerals, and squishy stuff.

Minerals are:


 * naturally-occurring
 * inorganic
 * solids
 * with a fixed chemical composition
 * and a fixed crystal structure.

Key minerals for a paleontologist include quartz, feldspar, mica, and calcite.

Rocks are made of minerals.


 * Fossils occur in sedimentary rocks, including sandstone and mudstone. Many clues to habitat conditions become locked in sedimentary rocks.


 * Igneous rocks (basalt, granite) and metamorphic rocks are important to paleontologists because they contain clues to big changes in Earth's past environments and landmasses.

Isotopes help geologists track time and environments.


 * In many chemical elements, the number of neutrons in the nucleus can vary.
 * Varied nuclear masses produce slightly different behaviors in these atoms.
 * Elements that have stable isotopes (the nucleus masses doesn't change in any individual atom) can record changes in environmental conditions, such as wet vs dry, hot vs cold, etc.
 * Elements that have radioactive isotopes (the nucleus mass can change in an individual atom) can record changes through time, such as the amount of time that passed since a mineral formed, or since it reached a certain temperature.

Finally, the Earth's rocky surface (lithosphere) is draped in a soggy blanket of water and gas (hydrosphere and atmosphere), and is permeated by living and dead things (biosphere).

Earth's Structure
Today, new observations of Earth's structure are made by geophysicists. Geoscientists use waves of earthquake energy, magnetics, gravity, and other fundamental physics tools to measure, compare, and model the most detailed structures of our planet.

This course will not cover the observations in detail, but we will overview Earth's structure.

The Earth has a crunchy crust that is always shifting and adjusting.