My Science Box

Summary
What's the big deal about rocks? They don' move, aren't flashy, and seem pretty useless to the untrained eye. To discover the beauty of rocks, one must look closer and learn how to read them. Geologists are rock detectives, discovering clues to the ancient past. If you know how to read them, rocks can tell an observant scientist about what a place looked like millions and even billions of years ago. This activity introduces the 3 main types of rocks and the processes that form them. Wax crayons are eroded into sediment, compacted into sedimentary rock, partially melted and pressed into metamorphic rock, and finally melted and cooled into igneous rock. This understanding is the basis of the rock cycle. In the Going Further section, there is a recipe for making your own sandstone, siltstone and conglomerate using sediments and a sodium silicate solution.

Objectives
Can describe the 3 major types of rock (sedimentary, metamorphic, and igneous) and discuss the relationships between them
Can diagram the rock cycle
Given one of the three major types of rock, can describe the geologic processes that formed it

Summary
Every rock holds clues about how it formed. Geologists are like rock detectives who know how to read the clues about a rock’s origins and the stories it can tell. In this activity, students first become specialists in one type of rock. Then, they meet specialists in other rock types to compare their rocks and teach the others about their rock’s history. This lesson is an opportunity for students to consolidate information from the previous lesson on the rock cycle, and begin to think like geologists. Ideally, the rocks selected for investigation are collected from the site of an upcoming geology field trip – such as to the Caldecott Tunnel or Mount Diablo. In this way, students gain experience identifying individual rocks and learning about the way in which each of the different rock types form. Then, on the field trip, students can apply their controlled classroom knowledge to real world geological history.

Summary
The study of rock layers, or stratigraphy, is a natural way to introduce students to the fundamental principles of geology and to lead into the idea of geologic time. In this lesson, students are introduced to Nicolas Steno’s 3 major laws of stratigraphy: the law of original horizontality, the law of superposition and the law of lateral continuity. Students also add their observations of sediment sorting from previous lessons (Soil Analysis, Erosion Patterns, and the Sediment Study Project) to generate a fourth “law” concerning depositional environment – the tiny grains in mudstone were most likely deposited in very still water like a lake or delta while large gravel in conglomerate was most likely deposited in fast moving rivers and streams. While this activity has students depositing sediments in clear plastic cups or Mason jars, it is recommended that the teacher simultaneously conduct the activity using a squeeze box like the one described by Eric Muller. In this way, when the student activity concludes, the teacher can take the activity further to show how layers can become folded and faulted by plate movements. This lesson is a natural extension of the Going Further activity from the Crayon Rock Cycle lesson where sediments are mixed with sodium silicate to create home-made sedimentary rocks.

Summary
This simple lesson gets students accustomed to reading a Geologic Time Scale and understanding the organization of the information contained in it by creating a Personal Time Scale using events from their own lives. Students list major life events then arrange them by relative time. Then, based on whatever organizational scheme makes the most sense to them, they divide their lives into eons. Each eon is divided into eras and each era into periods. Students can then view events in their own life with events in the history of Earth. In addition, they learn the difference between relative time (whether one event came before another) and absolute time (how many years ago something happened).

Summary
To apply students’ understanding of the rock cycle and basic principles of stratigraphy, I brought my students to the Caldecott Tunnel to investigate the local geology and piece together the geologic history of their backyard. The east side of the tunnel has an easily accessed road cut that displays a gorgeous example of a contact between older sedimentary rock layers and a more recent volcanic layer. The whole thing has been folded and faulted by the actions of the Hayward Fault, and thus the layers are no longer horizontal but at a sharp diagonal. My students drew pictures of the northern cliff face on the Orinda side of the tunnel then each student was assigned a rock layer to study in detail. When we got back to the classroom, we reassembled the data on the whiteboard, and made theories about the sequence of events that would bring about the rock layers we observed in the cliff. Finally, students drew pictures of what the area must have looked like at different parts of the timeline. This field trip led gracefully into the next segment of the unit on geologic time.

Photograph of the northern roadcut face at the Caldecott Tunnel from the field trip “Caldecott Tunnel between Oakland and Orinda” by Russell W. Graymer in "The Geology and Natural History of the San Francisco Bay Area: A Field-Trip Guidebook", edited by Philip W. Stoffer and Leslie C. Gordon.

Summary
The University of California Museum of Paleontology (UCMP) created a fabulous introduction to the geologic time scale on the web called “Understanding Geologic Time”. Students are led through a series of interactive web pages covering a wide range of earth history concepts: relative vs. absolute time, the law of superposition, radiometric dating, the geologic timescale, and the origins and evolution of life on Earth. While the teacher section includes assessment materials including a “Scavenger Hunt” activity, I have included an alternative worksheet for students to follow as they navigate through the website and some extra credit questions in UCMP’s online “Geology Wing” for students that finish early. Links to activities that teach radiometric dating are included in the Going Further section.

Summary
For students, a few days can feel like a very long time. Thus, my students have a hard time conceptualizing the difference between 1 thousand, 1 million and 1 billion years. In this activity, students develop a sense of just how long the geologic time scale really is by creating a to-scale geologic timeline. This lesson begins with students guessing how long ago different events happened – when the Earth was formed, when life began, when dinosaurs roamed, and when humans first appeared. Then students redraw the periods and eras of the Phanerozoic Eon to scale using adding machine tape (1 million years = 1 millimeter). Then a teacher created scroll containing the other eons: Proterozoic, Archean and Hadean is unrolled to give students a visual sense of just how long Earth history really is. Finally, there are some analogies for students to contemplate, such as when different events would have occurred if Earth history were condensed into a calendar year or into a cross country trip.

Summary
Fossils are extremely rare but also extremely exciting and rich with information about past life on Earth. In this lesson, students learn about the major types of fossils and how they form. They complete the lesson by illustrating and creating a “Choose Your Own Adventure” type story in which a Tyrannosaurus rex dies with 7 different possible endings, only one of which results in the discovery of its fossilized skeleton.

Summary

Cartoon by Chris Madden

What caused the extinction of the dinosaurs? Was it a massive meteor? Was it the result of tremendous volcanic activity that covered the globe in volcanic ash? Was it the effects of gradual climate change? Was it the result of plate tectonics? Students are given a set of evidence cards that state scientific discoveries about rocks from 65 million years ago and prediction cards that discuss the predicted effects of different events such as a meteor impact, a rise in carbon dioxide levels, and plate tectonics. Teams of students are charged with assembling this information into an overarching theory that best explains the evidence at hand. At the end of the period or the following period, teams present their theories to the whole group and enter into a debate about the cause or causes of the great dinosaur extinction.

Objectives
Can sort through evidence and come up with a scientific theory that best fits the data.
Can recognize whether evidence is consistent with a scientific theory.
Can use geologic evidence to propose theories about past life on earth.