University of Maryland Extension

Part 2: Geologic Timeline, A Context for Native Plants

Timeline Exercise

In the brick & mortar version of this class (the one where we all meet in person in a real building), MGs walk a geologic timeline on their way into the classroom. The timeline begins with the formation of the earth, 4.6 billion years ago, and ends with the present.  As the MGs walk the timeline, they are exposed to objects that represent events in geologic history. The events we have on the timeline for each class are ones that are relevant to the type of flora native to the region in which the class is held.

The objective of the walkable timeline is to allow each student to have an actual, physical experience of the length of time over which native plant communities have evolved. The timeline also allows the student to experience some of the milestone events that led to the evolution of Maryland's flora.

Most people learn better when they get to experience (discover, see, hear, taste, feel) new information for themselves. We’d like you to have the same type of experience, but to do that we’re going to need your help, we need you to actually follow the instructions.


  1. Please do not proceed with the rest of the class until you have completed the timeline.
  2. Allocate about 25 minutes to watch the video.
  3. If possible, find an activity, like walking, riding a stationery bike, riding on a train, that will give you a physical sense of progressing from point A to point B as you watch the video. Remember, you can watch videos on your smart phone (or someone else’s smart phone, for that matter). 
  4. As you watch the intricate chain of events unfold, think about how each one contributes to the creation of the flora present in your part of the state.
  5. Don’t try to take notes. The point isn’t to memorize geologic history, the point is to experience it.

Time to Think

Below are a few plant-related issues brought up by the timeline.  Answer the questions posed when you can, and when you can't, do some research.  Warning: Some of the questions posed by the timeline may not have answers. You do not need to turn in your answers.

  1. The video covers 4.6 billion years in 23 minutes. That's a pace of 3.3 million years per second.  If we slowed the pace down to 10,000 years per second, the video would be 333 times longer than it is now, and we'd still have only a minute to cover all of human history in the Americas.
  2. Ecologists tell us that we are currently experiencing the Earth's 6th mass extinction event.  Geologists tell us that there have been 5 prior mass extinction events.  An extinction event occurs when the rate of species creation is exceeded by the rate of species loss. A mass extinction rate occurs when the entire globe loses a large percentage of its species. 
  3. In each of Earth's previous extinction events, biodiversity eventually recovered.  It always takes several million years, and it always takes life in a new direction.  We could guess, based on this pattern, that biodiversity on Earth will eventually recover from the current extinction event as well.  So, you don't need to be concerned about the Earth, it will recover.  So what cause for concern is there?

Reading Assignment

Celebrate spring and learn about native plant ecology at the same time.  Read:

Introduction and Chapter One: Spring
from The Ecology of Maryland's Native Plants
by Louisa Thompson
It's about 15 pages.  Get it by clicking here.


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