ISGS - March 2012 Activity Highlights
ISGS - March 2012 Monthly Activities
Attendees listen to a talk at the Digital Mapping Techniques Workshop
Digital Mapping Techniques Workshop
The ISGS hosted the Digital Mapping Techniques Workshop at the University of Illinois Law Building May 20-23, 2012. Over 60 experts in geologic mapping, map data, and map dissemination were on hand from the United States Geological Survey, the Geological Survey of Canada, and twenty six state surveys. The workshop was designed to bring together scientists, cartographers, and Geographic Information System specialists, primarily from State and Federal Agencies, who are using digital techniques to create and manage geologic maps. (Contact: Dick Berg)
Hydraulic Fracturing Concerns Discussed
David Morse of the ISGS met in the Lt. Governor's office in the State House with officials from the Illinois EPA, and Illinois Departments of Agriculture, Public Health and Safety, Commerce and Economic Opportunity, and Natural Resources to discuss pending legislation and concerns about hydraulic fracturing of gas shales in Illinois. He described the fracturing process and the potential for use of large scale fracturing technology to recover natural gas from the New Albany Shale. Smaller scale fracturing of conventional oil and gas reservoirs has been conducted for the last 50 years without environmental problems. Surface containment of flow-back fluids from the very large fracturing operations and disclosure of the chemical constituents of hydraulic fracturing fluid were the main concerns discussed. (Contact: Dave Morse)
Educating 5th Graders about Geology Gains Awards
5th graders having fun on the Kickapoo trip
On April 9, the ISGS' Joan Crockett and Barb Stiff were awarded Certificates of Recognition from the Champaign Unit 4 School District for support of science education. They completed a field guide of the Kickapoo area, developed and conducted an exciting erosion demonstration on a point bar at Kickapoo, provided curriculum resources on the glacial geology in Illinois, and advised Unit 4 regarding development of a new 5th grade geology curriculum.
Joan and Barb had the able assistance of Dan Adomaitis, Curt Abert, Drew Phillips, and Dave Morse on the Kickapoo trip, and Dan and Curt contributed at Champaign curriculum planning meetings as well. The day in the field was covered by several ISGS sections contributing staff time to meet needs of a University of Illinois Public Engagement grant, that provided seed money to fund the effort. Curt supplied background curriculum materials for a rock and mineral identification activity, and Joan developed a guide for the activity. The activity subsequently has been modified and adopted for the Middle School geology program. Joan also prepared a guide to landforms, which also has been modified for use in the 5th grade curriculum.
Champaign Unit 4 plans to run field trips this fall for all thirty-six 5th grade classes. In addition, there have been requests from the University of Illinois Education Department to be included in the upcoming Fall trips. The field guide to Kickapoo has a much broader application, as it can be downloaded from the web, and may serve many school groups, youth organizations, families, and the people of Illinois for years to come. (Contact: Joan Crockett)
Southern Illinois Mega-erratic Revisited: a 2.66 Billion Year-old Find
ISGS staff member Dick Berg stands atop the erratic.
In December 2010, the ISGS reported on one of the largest glacial erratics (~22×10×11 feet with an estimated weight of ~100 tons) ever found in Illinois. But what made this finding unique was its location in southern Illinois (near Texico in Jefferson County), about 50 miles north of the southernmost extent of continental glaciation in the northern hemisphere. We reported that this erratic is an exotic rock that was brought to Illinois by continental glaciers about 150,000 years ago as ice sheets scoured, scraped, and plucked pieces of bedrock during their southward advance. The erratic was identified as being pink granite that most likely originated from the Canadian Shield north of Lakes Huron and Superior, and was transported to its far southern location.
Map of the likely path of the erratic
So that we could more definitively trace the erratic's origin and path to southern Illinois, small pieces of the erratic were removed and sent to the Arizona Laserchron Center at the University of Arizona, so that the age of the rock could be determined. The chosen technique was uranium-lead dating performed on the mineral zircon. This technique dates zircon ranging from ~ 1 million to 4.5 billion years old with a precision usually within 1%. An age with this method indicates when the granite crystallized as it cooled from molten rock deep in the earth (long prior to being transported to Illinois). The age determination is based on the fact that there are of two uranium isotopes contained in the mineral that decay and form two lead isotopes, with half-lives of 4.47 billion years and 704 million years respectively. By calculating the ratios of uranium and lead isotopes from more than 25 extracted zircon crystals, the age of the southern Illinois granite erratic was calculated to be 2.66 +/- .03 billion years old, more than half the age of the earth (~ 4.54 billion years old)! This places the rock's birth in the Archean Eon on the geologic time scale, the eon during which the oldest rocks on earth formed. Based on the known ages of granites in Canada, it can be concluded that our rock definitely originated from the Superior Province of the Canadian Shield, north of Lakes Huron and Superior, as previously suspected, and not from the Grenville Province to the east and northeast. We now believe that the rock travelled about 700 miles or so by glacial transport, from rural Ontario (northeast of Sault Ste. Marie) to its present location in Jefferson County, Illinois. This result confirms that glacial transport was most likely via the Lake Michigan basin. (Contact: Dave Grimley and Dick Berg)
EarthScope Arrives in Illinois
Transportable Array stations that have been or are presently occupied. The Illinois stations are shown in lighter blue.
Illinois is temporary host to 30 high-quality seismograph stations as part of the EarthScope Transportable Array project. EarthScope is a program of the National Science Foundation (NSF) that deploys thousands of seismic, GPS, and other geophysical instruments to study the structure and evolution of the North American continent and the processes that cause earthquakes and volcanic eruptions. One component of EarthScope is the Transportable Array, a network of 400 seismographs that are being placed in temporary sites across the United States from west to east. Transportable Array data are extremely useful for mapping the structure of the Earth's interior. After a residence time of two years, each instrument is picked up and moved to the next location on the eastern edge of the array. The array arrived in Illinois and western Indiana this past winter. The 30 stations in Illinois will remain until the summer of 2013. When completed, nearly 2000 locations will have been occupied throughout the U.S. during this program. Contact: Tim Larson
Location map of planned OIINK! seismometer deployment in two phases. The OIINK! array will fit within the larger EarthScope Transportable Array (TA) configuration. Inset map (lower right) is an image of the structure of the Precambrian surface in the study area and shows how OIINK! is designed to investigate the boundaries between the Ozark Plateau, the Illinois Basin, the Rough Creek Graben, and the Grenville Front.
OIINK!: A Telescope to Peer into Earth's Interior!
What the heck is OIINK!??? It is a new regional research project to study the details of the Earth's structure beneath the central United States. Three university research teams' from the University of Illinois, Indiana University, and Purdue University, together with the Illinois and Indiana state geological surveys, have teamed up to take on an ambitious project to better understand earthquakes and the geological structures that trigger them. This new research project, supported by the National Science Foundation, is playfully dubbed "OIINK!" after its principal study area: Ozarks Illinois INdiana Kentucky. The project involves the operation of a large seismic array centered over the Illinois Basin. It is being conducted in coordination with the deployment of a nationwide array of seismometers called the USArray The USArray is a component of a large experimental program called EarthScope, a national scientific experiment directed at understanding the geologic processes that create earthquakes and their relation to continental-scale geologic structures.
Our study area includes some of the world's best examples of geologic structures typical of the Earth's continental interiors (or "cratons"). The study will help us understand the structure of the Earth's crust and under-lying mantle, the causes of earthquakes within the interior of an otherwise stable craton, and the geologic history of the North American continent. Specifically, our array will span four of the major geologic structures that characterize the mid-continental area of the central US: the Ozark Dome of southeastern Missouri, the Illinois Basin of southern Illinois and Indiana, the Rough Creek Graben of western Kentucky, and the Grenville Front of central Kentucky. These features also include major fault zones such as the Wabash Valley Seismic Zone, the source of many earthquakes in the Midwest.
OIINK! array as it exists in May 2012. OIINK! stations are shown in violet circles and yellow circles and triangles. Stations shown as violet circles have been permitted. Vaults have been constructed at many of these stations. Stations shown as yellow have operating instruments: yellow circles are short period seismometers, yellow triangles are long period seismometers. OIINK! also uses data from the Transportable Array (red triangles and the existing network of permanently installed broadband seismometers (blue triangles).
Beginning in the summer of 2011, our researchers visited dozens of sites
in southern Illinois and southeastern Missouri, selecting sites for the
first 60 of the OIINK! array stations (violet and yellow symbols on the
2nd figure). We installed seismic vaults at 38 of the 60
sites. With only a fraction of the network instruments available, we
elected to install a "pilot network", consisting of 23 seismic stations
in the western half of the network. The pilot network consists of:
• 13 "short-period" seismometers (shown by yellow circles
on map) clustered along the Illinois-Missouri border that
are designed for recording local earthquakes, and
• 10 "broadband" seismometers (yellow triangles) along
an east-west line through the network that are designed
for recording both local and global earthquakes.
The pilot network, together with neighboring sites of the national USArray network (red triangles), are providing us with detailed data on earthquakes and earth structure along the Ozark Dome/Illinois Basin transition.
In its first several months of recording, the OIINK! network has already recorded several thousand seismic events. The recordings are dominated by the "artificial earthquakes" produced by blasting from neighboring quarries and surface mines, which occur at a rate of about 25 events/day. A major technical challenge is the discrimination of quarry and mine blasts from naturally occurring seismicity. The blasts are located in belts associated with coal mining along the eastern and western margins of the Illinois Basin and in the Rough Creek Graben.
We have recorded a small number of local natural seismic events and a much larger number of regional earthquakes from the New Madrid earthquake zone, as well as earthquakes from Oklahoma, Arkansas, Virginia, and Texas. We are able to record earthquakes as small as magnitude 2.0 for local earthquakes and magnitude 3.0 elsewhere in the region. Data from the OIINK! array are also being used to help us understand the geologic structures that produce these small earthquakes. Initial results from a sophisticated imaging technique called "teleseismic receiver function analysis" suggests that the Earth's crust and underlying mantle beneath the Ozark Plateau and the Illinois Basin vary considerably both in thickness and in physical properties. Contact: Tim Larson
Updated 08/06/2012 SLD