MGS geology.

Minnesota Geological Survey Podcasts


St. Paul Brickyards. Narrated by Mackenzie Gainey, MGS

The St. Paul Brickyards in Lilydale, St. Paul, MN is a local site for school groups and private citizens to collect fossils
from limestone and shales that were once part of an ocean floor. The area is managed by the St. Paul Parks and Recreation
. Check their web site for information on accessibility and permits. Search for Lilydale Park, St. Paul, MN.

For additional information on Minnesota fossils, check out the Minnesota At A Glance PDF, Fossil Collecting in the Twin Cities area.

Selecting a podcast from the ftp site will cause it to play if Quicktime or iTunes is present on your computer. To download the
podcast, right click (Windows) and select save link as or, control-click (Mac) and select copy then paste to the local drive. Obtain Quicktime or iTunes as a free download from Apple Computer for either Mac or Windows.

The podcasts available for download are in mp4a format and can be played with Apple iTunes or Quicktime. From iTunes
the mp4 can be loaded into portable devices such as an iPod for listening while at the site.

Minnesota's Evidence of an Ancient Meteorite Impact. Narrated by Mackenzie Gainey, MGS

Information contained in this podcast can also be downloaded as a PDF

For additional information on meteorite impacts:

Website describing 174 meteorite impacts world-wide. Developed and maintained by Planetary and Space Science Centre, University of New Brunswick, Fredericton, New Brunswick, Canada.

Collins, G.S., Melosh, J. H., Marcus, R.A., 2005, Earth impact effects program: A web-based computer program for calculating the regional environmental consequences of a meteoroid impact on Earth; Meteorite and Planetary Science 40:817-840.

The following images are included with the meteorite podcast, but are provided here in a larger format, with captions.

Figure 1
Figure 1. Artist interpretation of meteorite impact (not to scale).

Figure 2. Sudbury impact site and ejecta localities in the Lake Superior region. Dotted circle around Sudbury approximates the size of the original impact crater.
Figure 3. Layers of rock exposed near Gunflint Lake. Paleoproterozoic and Mesoproterozoic are geologic Eras.
Figure 4. Breccia containing large fragments of Gunflint Iron Formation. Hammer for scale is 16 inches long.
Figure 5. Accretionary lapilli showing concentric layering.
Figure 6. Reworked breccia containing iron-formation (reddish and gray-green fragments) and accretionary lapilli (gray spheres). Hammer head is 6 inches long.
Figure 7. This 25-foot thick layer (7 m) may represent a day (or less) of deposition during a 48 million-year time period from 1,878 to 1,830 million years ago (Ma).
Figure 8. Electron microprobe image of accretionary lapilli (by McSwiggen and Associates, PA).
Table 1. Calculated arrival times and effects at Gunflint Lake--480 miles (768 km) from Sudbury Impact.(See link to Earth impact effects program)
1. ~13 seconds Fireball 3rd degree burns, trees ignite
2. ~2-3 minutes Earthquakes Richter scale 10.2 at Sudbury, buildings collapse at Gunflint Lake
3. ~5-10 minutes Airborne ejecta arrives a layer 1-3 meters thick, with fragments <1 cm in size
4. ~40 minutes Air Blast Maximum wind speeds ~1,400 mph
5. ~1-2 hours Tsunami None of this magnitude