Carbon dioxide (CO2) is a major volcanic gas. It is invisible, odorless, and heavier than air. CO2 can accumulate in low-lying areas near volcanoes where unsuspecting people can be asphyxiated by walking into the invisible cloud of CO2 gas. This inquiry-based demonstration shows how CO2 gas produced from vinegar and baking soda displaces oxygen and sequentially snuffs candles representing different elevations.
This classroom activity combines information drawn from two sources: Pacific Northwest Seismic Network; and NOAAs Ocean Explorer web site. By modeling turbidite formation in a jar, students can investigate how “graded beds” are formed by turbulent undersea landslides and mudflows (turbidity currents). Turbidity currents were formed when past Cascadia great earthquakes shook the continental margin and sent torrents of sediment down submarine canyons and out onto the continental slope and rise. The resulting turbidite layers embedded in ocean floor sediments provide marine geologists with a record of past great Cascadia earthquakes. This story of scientific discovery was nicely told in a segment of Oregon Field Guide that can be viewed online at: http://www.opb.org/programs/ofg/segments/view/1715?q=tsunami
Full 8.5 inch by 11 inch map of ocean floor bathymetry off the coast of northern California, Oregon, and Washington. This map shows the locations of sediment cores that were examined for turbidite deposits produced by shaking of the continental margin during past great Cascadia earthquakes. The widespread distribution and age matching of these turbidite deposits is one line of evidence that past great Cascadia earthquakes (magnitude 8 and 9 earthquakes) have ruptured the full length of the Cascadia subduction zone every few centuries over the past few thousand years.
Native Americans have been living in the Pacific Northwest for thousands of years and have experienced numerous great Cascadia earthquakes. Because they are astute observers of landscape and nature, it should not be surprising that Native Americans recorded these earthquakes and the accompanying tsunamis in their oral histories. This “activity” is a resource that teachers can use to connect their students’ studies of Earth Science to history and culture by using Native Americans’ oral histories of past great Cascadia earthquakes and tsunamis. This collection of resources comes primarily from the work of Ruth S. Ludwin, University of Washington (Pacific Northwest Seismograph Network, PNSN) who has researched Native American stories along the coast of Cascadia. These oral traditions were also nicely described in the book The Orphan Tsunami of 1700 by Atwater and others.)
Teachers interested in Native American stories about geological events may wish to use the lesson plan Fire, Flood, and Fury under the Cascadia Volcanoes and Volcanic Hazards topic on the TOTLE web site.
This MS Word file contains teacher background information along with the Answer Key for the Pacific Northwest Tectonic Block Model Lesson Plan.
Chris Hedeen, Oregon City High School, developed this classroom activity that features a hands-on model of crustal block motions within the Pacific Northwest active continental margin. (The accompanying PDF by Philip Dinterman, Chris DuRoss, and Ray Wells describes construction of the model itself.) Through this activity, students can investigate the motions of crustal blocks in the Pacific Northwest and relate these to the tectonics of western North America. Ray Wells, a US Geological Survey geologist who is an expert on the tectonics and earthquake hazards of the Pacific Northwest, used paleomagnetic and GPS observations to determine how crustal blocks of this region slide past each other along boundaries marked by earthquake zones and how rocks of some blocks are faulted and folded as they are squeezed between blocks of stronger crust. The resulting earthquakes that occur on crustal faults near or immediately beneath densely populated cities of Oregon, Washington, and British Columbia are a major risk.
Instructions for building the Pacific Northwest Tectonics Block Model are provided in this PDF by Philip Dinterman, Chris DuRoss, and Ray Wells (US Geological Survey, Menlo Park, CA). The model is complex to build because it requires printing maps on a large-format printer, gluing maps to foam-core board, plasticizing maps, and many steps of construction. However, the Pacific Northwest Tectonics Block Model Lesson Plan can be done without building the model.
This Word file provides an editable student worksheet for the Episodic Tremor and Slip (ETS) Lesson Plan. If teachers wish to have their students do a portion of the ETS Lesson Plan, they can edit this file to produce a student worksheet for their modified classroom activity.
Roger Groom, Mt Tabor Middle School, developed this activity while working with Becca Walker at UNAVCO in Boulder, Colorado. Through this activity, students can learn about an exciting discovery made possible by invention of high-precision GPS receivers and deployment of these receivers across the Pacific Northwest. This activity can be used to illustrate how invention of new technologies can lead to new scientific discoveries that would have been impossible without the new instruments; a good lesson in how science works.
Some background: The friction between a subducting and an overriding plate of a subduction zone changes with depth. At shallow depths from the surface to 20 km depth, friction is high and the subducting boundary remains locked between very large earthquakes that occur every few decades or centuries. Deeper than about 40 km, friction on the subduction zone is very low and the subducting plate slides into the mantle without major earthquakes on the interface between the two converging plates. In some subduction zones, there is a transitional behavior called “episodic tremor and slip” (ETS) that takes place at intermediate depths of 20 to 40 km. ETS events on the Cascadia subduction zone occur when the Juan de Fuca Plate slips a centimeter or two farther beneath the North American Plate over a time interval from a few days to about two weeks in duration. This “slow slip” is accompanied by release of seismic waves (tremor) that are much longer in duration than seismic waves released by standard earthquakes. Because this process increases the stress on the locked shallow portion of the subduction zone, the probability of a great subduction zone earthquake may be higher during ETS events than at other times so this discovery has important implications for earthquake risk.
This 24″ wide by 36″ tall poster illustrates the violence and distribution of ground shaking produced by three types of Pacific Northwest earthquakes:
1. A magnitude 9 Cascadia subduction zone earthquake;
2. A “deep” earthquake within the Juan de Fuca Plate beneath the southern Puget Sound (e.g. like the 2001 Nisqually earthquake);
3. A magnitude 6.8 earthquake on a local crustal fault (e.g. the Portland Hills Fault).
Peak ground acceleration and likely building damage is illustrated for these three types of earthquakes.