When Did the Grand Canyon Begin to Form?

South Rim, Grand Canyon. Image courtesy of Kimberly Lightle.

This blog post draws from several news sources — washingtonpost.com, The New York Times, and Science Friday. All these sources have stories and photos related to a study published March 7, 2008, in Science by researchers Victor Polyak and Carol Hill (free registration is required to view this article). Science Friday features a 15-minute audio clip of an interview with Polyak. The research suggests that the Grand Canyon began forming 17 million years ago. However, for the past 100 years or so, geologists have agreed, based on a robust data corpus, that the Grand Canyon is probably five to six million years old, even though the rock from which it is carved is up to two billion years old. So what have Polyak and Hill done to upset this long-held theory of the Grand Canyon’s age?

To put it simply, they gathered new data and analyzed it using new technology. That is, they gathered rock samples called mammillaries from caves. These mammillaries are associated with ancient water tables and suggest previous levels of the water table. Polyak and Hill then analyzed these samples with improved rock-dating technology involving the radioactive decay of uranium to lead. The Grand Canyon began forming 17 million years ago at the western end in a west to east direction, and at a rather slow rate. Some time later, the east end of the Grand Canyon began forming from east to west, at a much more rapid rate. Eventually the two ends merged and the Colorado River emerged.

However, some scientists suggest Polyak and Hill’s methods and interpretations may be too narrow or incomplete. For example, their assumption that all the mammillaries examined originated in an ancient water table may not be a safe one. One critic noted that springs do occasionally emerge from the canyon walls and they could produce mammillaries as well. Another point of contention deals with the lack of 17-million-year-old sediment, which would be evidence of a 17-million-year-old river. Hill counter-argues that such sediment may not exist because the scale of the hypothesized 17 million-year-old, western river system would not produce sizable amounts of sediment. In addition, river erosion tends to destroy such potential evidence.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson
Estimating the age of the Grand Canyon is related to the History and Nature of Science, Science as Inquiry, and the Earth and Space Science content standards of the National Science Education Standards. With respect to the first two standards, several themes emerge. The researchers proposed using improved laboratory techniques and new data sources to make an estimate of the age of the Grand Canyon. In this way, they demonstrated the idea that science advances with new technologies. Science also seeks disconfirming evidence to existing theories as a means of gaining increased certainty regarding what we know about the natural world. If scientists fail in their attempt to find disconfirming evidence, they have succeeded in strengthening the existing theory. If they find disconfirming evidence of existing theories, then they pave the way to new lines of research, which must be further investigated. Eventually, existing theories may be either supplanted or revised in light of the new evidence, or they may be strengthened should the new evidence turn out to be unreliable or invalid.

The news sources related to this research also provide “air time” for scientists who argue alternate interpretations of Polyak and Hill’s data and who point out that Polyak and Hill may be ignoring some facts that impact their conclusion. These presentations underscore the role of argumentation and evidence based logic in advancing scientific knowledge as well as the social nature of science.

Ask your students if they know how old the Grand Canyon is. Ask them if they imagine someone knows, even if they don’t. From here, the discussion is going to go in one of two directions: (1) If they imagine someone knows, how do students imagine the someone knows how old the Grand Canyon is; what kind of evidence might have been used? Entertain all student contributions and stipulate that the students provide some justification for their response. You may need to do quite a bit of guiding and scaffolding here to lead students to support only evidence-based and logical responses. (2) If students imagine no one really knows, ask why not; what prevents human beings from knowing?

Depending on your students’ background knowledge and context you can relate the discussion to a variety of instructional goals and learning objectives. Do you want to emphasize the nature of science, evidence-based argumentation, and the social aspects of doing science? Then choose excerpts from Science Friday’s interview, which highlight these aspects in the context of real scientists doing real science and devise discussion questions for your students to reflect upon in order to increase their awareness of the nature of science.

Maybe you want to highlight some methods of science like rock dating. Perhaps you can use this opportunity to illustrate how new questions can emerge from gathering evidence intended to answer another question, as is illustrated in the final paragraph of the washintonpost.com story.

Or maybe you want to give students practice with science literacy. Put students in small groups and give each group one of the three sources listed in the first paragraph of this blog. Devise two or three open-ended questions for each group to discuss and reach consensus. Have the students jigsaw into new groups and share the consensus of their first group. How does each student now understand the issue of determining the age of the Grand Canyon? How does this issue intersect with the bigger idea of the nature of science?


We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. This post was originally written by Mary LeFever and published March 14, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 11/16/2011 by Kimberly Lightle.

Earthquake Resources

With the recent earthquakes in Colorado and Virginia it seemed timely to share some of the previous blog posts and other Middle School Portal 2 (MSP2) resources on earthquakes and plate tectonics. The US Geological Survey website tells us that earthquakes are occurring all the time, but it is both their intensity and the depth at which they occur that determines the effect and damage they can cause. The site also has a very interesting FAQ section on earthquakes. In addition, the MPS2 Resource Guide on Plate Tectonics is an excellent primer on this subject with many high-quality resources. Also, you may want to revisit a previous blog post on this subject related to the earthquake in Japan entitled Disaster in Japan.

Hot Spots (Even in Cold Places)

Did you know that there’s an active volcano in Antarctica?

Mt. Erebus, the world’s southernmost active volcano, is located on Ross Island, just off the coast of Antarctica in the Ross Sea. Part of the Ring of Fire, Mt. Erebus is located along the boundary of the Scotia and Antarctic tectonic plates.

Students may be surprised to learn that an active volcano can be found in such a cold location. Yet the heat of a volcano and its lava has nothing to do with weather and climate and everything to do with Earth’s internal structure and the theory of plate tectonics. The connection between plate movement and volcanic activity is part of the typical middle school curriculum and included in the Earth and Space Science content standard of the National Science Education Standards for grades 5-8.

Too often, students’ experience with volcanoes comes in the form of baking soda/vinegar models, which can actually lead to the formation of misconceptions. Instead, use the following resources to help your students more accurately model and visualize volcanic activity.

Volcanoes
http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.lp_volcanoes/NSDL Annotation
In this multi-day lesson, students investigate the processes that build volcanoes, the factors that influence different eruption types, and the threats volcanoes pose to their surrounding environments. After exploring these characteristics, students use what they have learned to identify physical features and eruption types in some real-life documented volcanic episodes. The lesson includes the use of many multimedia resources from the Teacher’s Domain collection.

Mt. Erebus Volcano Observatory
http://erebus.nmt.edu/
The MEVO web site provides background knowledge, video, photos, and other resources about the world’s southernmost active volcano.

Volcanology
http://www.spacegrant.hawaii.edu/class_acts/VolcanologyDoc.html
Five lessons from the Hawai’i Space Grant Consortium provide opportunities for students to learn about magma’s movement inside volcanoes, the stratigraphy of lava flows, structures formed by lava, how particle size affects the angle of a volcano’s slope, and how to measure a liquid’s viscosity. Each lesson includes separate student and teacher pages.

Exploring the Environment: Volcanoes
http://www.cotf.edu/ete/modules/volcanoes/volcano.htmlNSDL Annotation
A problem-based learning module in which students use online information to make decisions regarding four well known volcanoes. Designed for students in grades 7-12, but could be used with younger students needing additional challenge.

Plate Tectonics: Moving Middle School Science
http://msteacher.org/epubs/science/science1/science.aspxNSDL Annotation
The study of volcanoes at the middle school level is incomplete without a connection to the theory of plate tectonics. Discover background information, animations, activities, and standards alignment.

We Need Your Help

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. You can also request email notification when new content is posted (see right navigation bar).

Let us know what you think and tell us how we can serve you better. We want your feedback on all of the NSDL Middle School Portal science publications. Email us at msp@msteacher.org.

The International Polar Year

On March 1, 2007, teachers and students around the world are invited to help launch the International Polar Year 2007-2008 (IPY), a scientific program focused on the Arctic and the Antarctic. From March 2007 to March 2009, thousands of scientists from over 60 nations will be involved in more than 200 projects examining physical, biological and social research topics. IPY is an unprecedented opportunity for teachers and students to follow cutting-edge science.

The official web site, International Polar Year, includes a blog where teachers can share activities and ideas. An online flyer titled Breaking the Ice describes activities that can be carried out in classrooms. Here are resources that will help your students understand the IPY’s study of the impact of changes in earth’s ice and snow on our planet and our lives.

What Organisms Live in Antarctica?NSDL Annotation
In these activities, students will discover the characteristics that enable Antarctica’s many life forms to live in this continent of extreme cold, wind, and extended periods of light and darkness. In a weeklong unit, students research how flora and fauna have adapted to thrive in Antarctica and use their knowledge to create imaginary polar organisms.

Polar Bear CentralNSDL Annotation
From the World Wildlife Fund (WWF) Canada, this web site is all about the giant arctic bears, their habitat, and behavior. Also, you’ll find out what threatens the polar bears’ survival and how WWF is working to protect them.

To the Ends of the Earth: Research in Polar SeasNSDL Annotation
In this lesson, students will discover the differences between Arctic and Antarctic terrains, the hardships polar explorers endured, and how modern technologies have expedited polar exploration.

Melting Polar: Antarctica NSDL Annotation
This two-minute sound segment from Pulse of the Planet discusses the effect of global warming at the South Pole. It is thought that the effect would be different from that at the North Pole because the South Pole icecap is located over land.

Impact of Climate Warming on Polar Ice Sheets Confirmed
This page discusses recent changes in polar ice. Excellent photos are included.

We Need Your Help

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. You can also request email notification when new content is posted (see right navigation bar).

Let us know what you think and tell us how we can serve you better. We want your feedback on all of the NSDL Middle School PortalNSDL Annotation publications. Email us at msp@msteacher.org.

Fossil Formation

The National Science Education Standards Life Science Content Standard mentions that fossils indicate extinct species and contribute to an understanding of evolution and diversity. The Earth and Space Sciences Content Standard tells us they provide clues about past environments. But what is a fossil? How does it form? The processes can be complex. An understanding of fossil formation will enable accurate student conceptions of related science concepts including methods of science in geology, paleontology, and evolution.

Becoming a Fossil
This short video clip from NOVA is accompanied by an essay and discussion questions all describing the rare conditions under which fossils form and are found. Free registration is required.

What is a Fossil? How Do They Form?
This page provides a concise explanation and illustrations of Ammonites fossil formation via permineralization – when the pores of the plant or animal remains are impregnated by minerals. When this happens, the original shape of the object is not changed.

Fossilization
The information on this page is good, if you can bear the bright green background! It includes some vocabulary and how environmental conditions determine the fossil category. There are useful links at the bottom as well to teacher resources.

Fossils, Rocks, and Time
This online book, published by the U. S. Geological Survey, discusses the use of fossils in determining the age of rocks. The book covers how to place events in correct temporal order, a description of the geologic time scale, the use of fossils to indicate rock ages, the law of fossil succession, index fossils, and radioactive dating.


We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. Post updated 11/14/2011.