On the island of Hawaii, residents are all too familiar with lava flows encroaching on their properties. In 1986, the town of Kalapana was overun by flows destorying homes, vehicles, roads and vegetation- leaving swaths of unwelcome basalt throughout this Hawaiian community. Creeping at speeds of several kilometers/hour, you can certainly out-walk these- but with temperatures of active flows between 500 and 1400 C, they are extremely dangerous forces of nature. The USGS has a day by day video/photo chronology you can follow here.
The perfect counter-pose to a year of teaching? Two glorious mornings in the field, learning about our community’s amazing geology. As part of Poudre School District’s Summer Institute, teachers from across grade levels and schools, joined together for a fun day in the foothills west of Fort Collins. Each of the two mornings was followed by afternoon classroom trainings where teachers used the days’ photos, video clips, and notes to construct virtual field trips for their students. Lessons included stream erosion and deposition along the modern Poudre River, explanation of mountain building, faulting and folding, and of course, the obligatory time travel. This group visited the ‘ancient’ Poudre River dating back 300 million years to the time of the Ancestral Rockies. Capping the experience was a close look at shale beds which are both economic (shale gas and oil) and a hazard (when homes are built on their unstable slopes). Thanks to Dee Dee Wright, Adam McBride and guest scientist Neil Sherrod for their support and teaching.
High clouds obscure the lowest path of the sun during this year’s winter solstice. Looking forward to the companion video on June 21.
A few observations about our current Front Range flooding. First, the rain is welcome as the area is still in a moderate drought condition but wow, enough is enough! I measured well over 4.5 inches at my house but south of here- in the Boulder-Longmont area, a few observers reported in excess of 14 inches over the duration of the storm. Second, all the rain was accompanied by mild temperatures and little or very light winds. Not much in the way of downed power lines- though power and cell service were knocked out in many places. Folks from the East or Gulf Coasts who are used to September tropical storms must think it a bit strange. Third, and most meaningful to me are the violent bursts of water rushing down our mountain-front canyons, doing exactly what they do (geologically speaking)—vigorously eroding the land. Unlike historic flood events I can remember, this storm is quite regional, impacting the entire Front Range of Colorado, a corridor of about 150 miles.
Big erosional events like these make me appreciate the power of moving water. The origin of canyons, such as those along the Front Range, are easier to understand if you do the math…. 1 meter of erosion every 1000 years (if this is a true 1000 year storm) in a million years equates to roughly 1,000 meters or more than 3,000 feet of downcutting. Of course, downcutting is an everyday event combined with the fact that the Rockies are still slowly rising albeit at a much slower rate. And, if you’re wondering, the Grand Canyon is about 6 million years old.
Debris flows are a type of landslide where a liquified jumble of earth and plant materials form a fast moving mixture following a rain event, dam breach or rapid snow or glacier melting ( from a volcanic eruption, for example). Here, people anticipated the flow along a dry creek bed and essentially ‘chased’ the event down as a storm chaser would track down severe weather such as an outbreak of tornadoes. Is this safe?…not at all! but what’s so eerie is the way the flow occurs well after the rain storm. This reminds me of the way tsunami waves devastate coastal areas, many hours after large submarine earthquakes generate their initial jolt.
Its fun to watch each month’s weather and water patterns emerge into a story. This Spring in Fort Collins, its been warm and dry and we’ve coaxed (and coached) elementary students to report on these topics as they observe and report daily precip (or lack thereof) measurements to CoCORahs. When we post these on Poudre School District’s website, we usually get a handful of views. March’s report apparently struck a chord. Watch Seattle meteorologist Sc0tt Sistek’s post to see what I mean. My guess? I think it was the missing teeth, cookies, and overall cuteness of these wonderful second graders. Thanks to Dunn Elementary teachers Lori Ellendorff and Deborah Taylor for supplying the talent, and Matt Gohl (as usual) for great editing and graphics. Eva Jane and Charlotte have a future career in TV meteorology!
What is the “Great Unconformity”?
Thanks to Dr. John Ridley of CSU Geology and our intrepid Northern Colorado Geology Group, we braved cool temperatures and rain to learn more about our local geology. So, what exactly is the Great Unconformity? Not-fitting-in is partly the answer. In geology-speak, an unconformity represents a break in the geologic record of earth history. Here in the Front Range of Colorado, we live minutes away from this amazing geologic feature- namely the contact between 300 million year old Fountain Formation (red, horizontal strata) and the underlying nearly vertically tilted 1.7 billion year old Precambrian schists and granites. Although sporadically visible in places along the Front Range, the Great Unconformity is beautifully exposed west of Loveland near Pinewood Reservoir.
What always amazes me about this is the story it tells about a very ancient mountain range (1. 7 billion year old schists and granite) whose surface was reworked by 300 million year old rivers -now red sandstone). Although the time interval between these 2 events is still over 1400 million years, we can unravel what happened with astonishing clarity right here! Geology is as much about what is left behind as is what is missing. In this case– a lot! That’s what unconformities are all about- missing pages of earth history. So, next time you’re hiking in the foothills see if you can predict where this contact occurs. Or if you’re attending a show at Red Rocks- come early and take a few minutes to visit the Precambrian-Fountain contact which is marked by a plaque behind the amphitheater. Unconformities rule!
For fans of Walking through The Water Year, here are Scott and Matt’s finest minutes!
Great job guys!