|Posted on September 9, 2016 at 8:00 AM||comments (1)|
IDGS's Graduate Geologist, Brandy Barnes, is out west for the American Institute of Professional Geologists (AIPG) Annual Conference. She is sending us contributions to our blog to make us jealous! Here is her entry from last week. Enjoy! A Florida Geologist's adventure in the Colorado Front Range "A year ago, I attended the 2015 American Institute of Professional Geologist (AIPG) Annual Meeting in Anchorage, Alaska, where I was completely mesmerized by the beauty of the Alaskan Range, glaciers, and the backdrop of the beautiful gulf. Now, that I am about to attend the 2016 AIPG Annual Meeting in Santa Fe, I have come to visit the Denver, Colorado region where the Front Range of the Rockies is just a short drive away. The largest smile came over my face after seeing the Rockies for the first time since 2014. My first adventure in the area was to Rocky Mountain National Park. As we entered Loveland, CO, we passed an area that was heavily affected by the 2013 Colorado Flood. Due to consolidated volcanic and metamorphic rock in the region, water was not able to infiltrate the ground; therefore fractures in the rock provided a path of least resistance into a downward sloping region of the Big Thompson River. A similar flood also happened in 1976 that killed 114 people, in 2013, 8 people died. It was devastating to those living in the effected region with hundreds of homes being marked condemned. To this day, many homes still have large X's on the house indicating that they are still uninhabitable. It is remarkable to see the effects of the flood that has shaped the river and changed the lives of those in the state. The drive through the Rocky Mountain National Park is nothing short of breath taking. From the sky scraping mountains to the wildlife, it is worth taking the time for a visit. A word to the wise for those of us living at sea- level, bring plenty of water and take slower breaths. Altitude sickness can take you off guard, especially when you try to exert yourself too quickly. I was quite fine, but I did notice some changes in my depth perception as we reached 11,900 ft. Other amazing geologic sites close to the Denver area and within the Front Range is Red Rocks and Dinosaur Ridge. They are side by side and show perfect textbook geology for an angular unconformity and a geomorphic hogback. Red Rocks is a venue for a large collection of concert series and movie events, all while being captivated by a beautiful landscape. Dinosaur Ridge is a segment of the Dakota hogback where a variety of dinosaurs and prehistoric invertebrates have been discovered in the famous Morrison Foundation among the sandstone and shale layers. There is also a road outcrop along I-70 east that shows the Cretaceous- Paleogene boundary, which marks the extinction of the dinosaurs."
|Posted on September 1, 2016 at 1:55 PM||comments (1)|
As Tropical Storm Hermine, possibly soon-to-be Hurricane Hermine, bowls into Florida, we are expecting several inches of rain. Its been a pretty average summer for rainfall already, and we've been dealing with some pretty wet sites for drilling just lately. Our Florida "wet and dry" seasons can lead to some dramatic changes underground too. Daily rains and tropical systems can be a driving force for sinkhole formation, particularly in areas where stormwater runoff is concentrated, such as dry retention ponds and ditches. The localized increase in drainage down through the soil below a dry retention pond leads to a process called "suffusion", which is the removal of fine particles from the soil. If there are holes in the limestone below and the water can flow into the limestone, then this can be a mechanism for sinkhole formation. Sinkholes can also form in the aftermath of heavy rainfall. As groundwater levels rise through the rainy season, the load that the soil resting on the limestone at depth "feels" reduces, through a process akin to buoyancy. As the groundwater level falls back again, then the load of the soil is reapplied, and sometimes, if there is a cavity in the limestone close to the top of rock, then that lifting and relaxing of the soil can cause the soil and/or the top of rock to weaken and fail, leading to sudden sinkhole formation. Tropical Storm Debby in 2012 was responsible for dozens of collapse sinkholes, many of which formed in this way. We at IDGS can help. We can act as "first responders" with our drilling and GPR equipment if a sinkhole either forms or is suspected after heavy rain. Knowing how high the water table can rise is also a skill that helps in the design of stormwater ponds. If a pond is designed to be dry, then no-one wants to see cat tails growing in it at the end of the wet season. Also, if the pond is designed to be wet, no one wants to see a swampy mess instead of a nice body of water at the end of the rainy season. Predicting the "seasonal high groundwater" is key, and its as much art as science! We at IDGS can help here too. We can estimate seasonal low and high groundwater table by direct measurement or by installing monitoring pipes in boreholes, to see where the "stabilized" groundwater rests. We can also find signs of high groundwater, such as staining and mottling of soils. GPR can also be used on a broader scale, since the GPR signal is damped down when it enters saturated soil. Hope that everyone stays safe during the storm! David Wilshaw, MS, PG IDGS