Then Now

4.5 Billion Years! It is very difficult for humans to appreciate time beyond that of one or two generations, much less hundreds, thousands, millions and billions of years. Today we’ll be doing an activity called the “Time Scale Metaphor” to try to get a grip on this thing called time. If Geologic Time were represented by this frosty delicious root beer float, where would the first oxygen atmosphere have been evident? Origin of the Earth Known age of past event = Time Scale Metaphor Known age of the EarthMetaphor Maximum Measurement 20 cm 2 billion years bp = ____X_____ 4.6 billion years bp 20 cm Present Day X = 8.7 cm Earth’s First Oxygen Atmosphere

So…let’s do the math… 2 billion years bp = ____X_____ 4.6 billion years bp 20 cm So, now all you have to do is cross multiply, and solve for X 2,000,000,000 x 20 = 40,000,000,000 4,600,000,000 x X = 4,600,000,000X 4,600,000,000X = 40,000,000,000 4,600,000,000 X = X = 8.7 cm So, what do you know? You know the age of the Earth is 4.6 billion years. You know the time of Earth’s first oxygen atmosphere is 2 billion years. You know the height of the root beer float is 20 cm. At this point, you know that if all of geologic time is represented by this 20 cm object, that the oxygen atmosphere would have appeared approximately 8.7 cm from the bottom! Measure 8.7 cm and there you have it!

For this activity, you will be working in groups of two. Decide on, and design a time scale metaphor of your own that is true to scale, and reflects eight important events in the history of the Earth. You will get a poster- sized sticky paper to do this on. Design, name and measure your metaphor Choose and research the times of your 8 important events in Earth’s history Calculate the length (given your metaphor’s size) of each event from the bottom of your metaphor Draw in the timeline of each event on your metaphor, SHOWING all calculations!!!!! Tell why your group chose this particular metaphor (in a short paragraph (upper right hand corner) Each of you will get a colorful 3x5 index card. Write a brief reflection on this experience, including where humans fit in the grand scheme of things! Have fun. Be creative! No metaphor is too silly, as long as it is school appropriate, and your calculations are correct. Your group’s choice should have meaning to you. I appreciate unusual and distinctive efforts…creativity is rewarded! Root beer floats are off limits, however!

Years AgoImportant Event 4.6 billion yearsOrigin of the Earth 3.9 billion yearsOldest rocks 3.8 billion yearsFirst life 2 billion yearsFirst oxygen atmosphere 900 million yearsFirst multicellular life 510 million yearsFirst fish 458 million yearsFirst land plants 375 million yearsFirst amphibians 245 million yearsLargest mass extinction ever 200 million yearsFirst mammals 160 million yearsFirst birds 130 million yearsFirst flowering plants 65 million yearsKT extinction 3.4 million yearsEarly hominids 600 thousand yearsHomo erectus dominates 100 thousand yearsHomo sapiens dominates 15,000Glacial ice sheets retreat in last ice age 608 yearsColumbus lands in New World ??Your birthday This isn’t even close to an all-inclusive list, so do some research, and find some events of your own! There are a great deal of important events not listed here. I hope to see some interesting ones in your metaphor! You have the rest of class today to work on your idea…and Monday and Tuesday. This project is due on Tuesday, at the end of class.