## ESCI 102 Homework #1: Geologic Time (10 pts) Due: 9:00 AM, Wednesday, 02/09/05

Understanding the events of Earth's history is crucial to interpreting and describing the processes that created the events. It is, however, very difficult for humans to appreciate time beyond that of one or two generations, much less hundreds, thousands, millions and billions of years. In this homework exercise you will relate eight events of Earth's history to a common and easy-to-understand object or item. The goal is to explain the hard-to-comprehend times of the events (geologic time) into a framework with which your colleagues can relate (simple metaphor).

The general formulation to create your geologic time metaphor is:

 Known age of past event Known age of the Earth = UNKNOWN equivalent Maximum measurement in metaphor

For example, we can use the distance of a marathon, 26.2 miles, in our metaphor. This will allow us to think about events in Earth's history relative to how far or near we are from finishing the marathon. Let's compare significant oxygen in Earth's atmosphere to the marathon.

 Known first oxygen (2.2x109 years) Known age of the Earth (4.6x109 years) = Distance from finish line (X) Length of marathon (26.2 miles)

We can rearrange our general equation to get

X = (2.2 x 109 years)(26.2 miles)/(4.6 x 109 years).

This yields X = 12.5 miles, or that the first significant oxygen on Earth is equivalent to 12.5 miles from the finish line of the marathon. If we carry out the same calculation for time of modern humans, it corresponds to being 14 inches from the finish line. That's pretty far along in the race.

1. Define your metaphor scale. Pick something with which you can easily relate. You can pick some important distance, volume, mass, weight, decibel, etc. The only rule is that you cannot use a marathon, because that was my choice.
2. Show all of your math calculations. These can be handwritten or typed. Make sure to include units in all calculations.
3. Include the following eight events in your metaphor. Feel free to add more if you want.

 4.6 billion years Formation of Earth 3.8 billion years First life 2.2 billion years Significant oxygen in atmosphere 1.1 billion years Oldest Texas rocks 230 million years First dinosaurs 65 million years Extinction of dinosaurs 150,000 years Homo sapiens first appear 40,000 years Modern humans

4. Write a short essay (less than 250 words) that explains why you chose your metaphor and what two key observations of your metaphor are.

Grading will be based on the following scale

Formatting (2 pts): Essay is typed in 12 point font (Times, Times New Roman, Helvetica, or Geneva) with 1 inch margins around the page. Your name, date, course name, and assignment number (Homework #1) are included on the page. Include the honor pledge (On my honor, I have neither given nor received any unauthorized aid on this assignment) at the bottom of the assignment and sign it.

Mathematical Calculations (3 pts): You showed all of your work including units. Your calculations are correct. Calculations can be typed or handwritten.

Essay (5 pts): You clearly explain why you chose your metaphor (i.e. why is it important to you?, why can people relate to it?). You incorporate your math answers into the essay. You define two key observations from your metaphor and explain why they are important.