Unit 4: Rocks, don't take them for granite - Geologic Time

Unit 4 Goals & Resources
Unit 4 Vocabulary (Student Created Glossary of Terms)


Have humans permanently changed the planet?

This question has started a debate of *when* in time we are living---meaning, where on the geologic time scale do we find ourselves right now?

The Basic Geologic Time Scale Based on Rock Layers

If you have not heard about this mother of all timelines, the geologic time scale is divided into units based on events which took place in Earth's 4.6 billion-year-old history.  Boundaries in the timeline are decided by major changes in rock layers.

Many people agree that we are currently in the Holocene Epoch, in the Quaternary Period, in the Cenozoic Era in the Phanerozoic Eon.  The Holocene Epoch began right at the end of the last ice age over 11,000 years ago.  It was during this time we can see major changes in rock data. 

However, according to some scientists at the International Union of Geological Sciences we have now left the Holocene epoch and now are in a NEW epoch called the Anthropocene.  Anthropo meaning "man" and cene meaning "new."

Scientists say that humans have made such an impact on our planet that we can see it in the soil.  For example, if we look at rock layers worldwide, we would find a change in the radioactivity in the soil in 1964.  It was during this time when nuclear weapons were being tested.  Some scientists use this and many other indicators as evidence that we have permanently changed the planet in such a way that we have brought about a new epoch.

In this upcoming unit we will be looking at rocks for evidence to the past.  We will be asking questions like how does the Earth change over time and how can rock types and rock layers be clues to the past?  We will look at landforms and study how erosion and plate boundaries have changed our earth over time.  

Hopefully by the end of this unit, we will gain a better understanding of not just where we are in the universe, but WHEN we are in time.

Read more about the Anothropocene on Science News for Students