Highway engineering, aquatic ecosystems and a little bit of gold

A second installment of Geology begets biology

This is a view looking east towards the Continental Divide in Summit County Colorado. The highway snaking up the hill is Interstate 70. The highway bottoms out at 8900 feet and then climbs steadily to 11,150 feet where the road enters the Eisenhower Tunnel and makes its way under the Continental Divide to the east slope.

The original plans had the tunnel a few miles west and a couple of thousand feet below its current placement. However, before construction began, the bean counters started to complain about the length of the tunnel and asked if there could be another placement for the bore. So, apparently the powers that were decided that the geology in the mountain should all be somewhat similar and decided to drill the tunnel in its present configuration. So, the highway now climbs up the Straight Creek drainage to the 11,150 foot elevation and then makes its way east.

The problem with this plan is the gradient of the highway exceeds the Interstate standards and requires massive amounts of sand to keep the highway open. It is just too steep on those icy days.

Normally, a high country stream like this is relatively sediment poor and would be able to easily transport any sediment it receives from erosion. However, now as spring arrives and the snow melts, huge amounts of sand are washed into Straight Creek severely impacting water quality. The towns of Dillon CO. and Dillon Valley CO. rely on this watershed for their potable water. In addition, Straight Creek runs into the Blue River with its gold medal fisheries.

In the early 1990's my biology classes spent some quality time in Straight Creek doing pebble counts and macro-invertebrate census collections. Yes, the water was quite cold. Our findings: There were no macro-invertebrates as their habitat had been inundated by feet of sand. The pebbles we found, were all sand grains. No matter our findings, this was a wonderful experience for a group of high school sophomores and our data ended up in someone's Master's thesis.

By now, the Colorado transportation department, local water quality agencies and the state wildlife agency saw the problem and created a series of check dams and sedimentation ponds to catch the sand. In 1993, over 1100 tons of sand were removed from the ponds, about 10% of the total sand applied. Since then, more check dams and sedimentation ponds have been built and by 2000, the majority of sand has been kept from entering the creek. This is an incredible long term maintenance process that in the long run, costs more than the longer tunnel would have back in the 1970's

Cold across the Country

Cool image of the cold across much of the country.

Thank you weather underground.

Geology begets biology. North facing vs. South facing slopes

I taught High School biology for a long time, almost my whole K-12 career. Of course, that meant my biology classes had a decidedly geological slant to them. One concept I tried to instill in my biology students was that the literal underpinnings of the ecosystem was the underlying geology.

I called these explorations "Geology begets Biology"

One idea that seems simple but created problems with many students was north facing slopes vs. south facing slopes. Both sides of a hill receive approximately the same amount of precipitation, have similar soils and experience the same temperatures but can appear very different from each other. However, the south facing slopes receive more direct sunlight and snow will melt faster, soil moisture will evaporate faster creating a dryer micro climate than the shady north facing slope which might be only meters away. The slower evaporation on the north side means that plants (that biology connection) will have more available moisture. With the snow melting at a slower rate, there is more water available longer in to the spring.

Ultimately, the species of plants found on south facing slopes will be more drought tolerant while their north facing cousins less skilled at surviving with low water amounts. Here, in Colorado's southern mountains, the north facing slopes are full of large evergreen trees, while the south side has more shrubs like the ubiquitous sage brush. So, in just a glance we should be able to roughly decide on "north" even without a compass.

In the foreground, the grassy slope is facing south and west while the heavily treed area is more north and east.

Notice the scrub oak. What you can't experience is the snow depth under the oak is only a few inches.
Looking across the gully at the fully melted south facing slope. I was traveling on the north facing slope in 8-10 inches of snow from a recent storm while the other side is clear.
Again, looking across the gully at the melted out slope. I was in the shade of a large Ponderosa pine tree. The south facing side is home to a large population of scrub oak trees

A visit to our Grandson and the Pacific Plate

We spent the MLK weekend visiting our almost one year old grandson (and family) in California. One day, we traveled across the Santa Cruz mountains to the ocean and visited a small state park, Natural Bridges State Beach with its namesake natural bridge sitting just a little bit off shore. I will admit, I was too busy making faces and goofy sounds and generally playing grandfather with the baby to notice when we crossed over from the North American Plate to the Pacific Plate. I guess I will pay more attention on the next visit.

Once at the state park we spent some time exploring the beach. Having spent most of my geology career in Colorado and Utah, I find visiting a current beach to be lots of fun. The beaches I usually frequent were sea side back in the Permian.
The rock was a fun mudstone. A very fine grained sedimentary rock, Miocene in age. Again, I am used to pretty soft sedimentary rock in the canyons of Utah. This mudstone was, pardon the expression, rock hard! The cementing agent of SiO2 has created a very erosion resistant rock that made some great tide pools, ocean side cliffs and
... of course the natural bridges. In the recent (historical) past there were three bridges present. Two have succumbed to the power of erosion leaving the sole remaining bridge, for now. Reading a web site from the University at Santa Cruz the author suggests that the bridges have been transformed from a natural wonder into an educational resource.As for being on the Pacific plate. It didn't feel very different, but I thought I could just faintly detect a little more northward motion instead of the constant westward traveling I have been doing my whole life.

The earth will survive

I had the chance to visit an upper elementary classroom just a few days ago. While there I shared how the earth's climate has changed over time. I led them through the idea that we have all kinds of clues about past climate by looking at rocks. So, we examined hand samples of sandstone, shale and limestone and compared the clues from each rock type. We discussed how differences in temperature, atmosphere, proximity to water can change how a rock looks (not bad for a group of kids with no chemistry in their academic history) And if the weather cooperated we would have taken a field trip to some nearby cliffs to see the story they tell.

One student, obviously getting information from her parents, decided to trap me about climate change. She was pretty smug when I replied that yes, the planet itself has survived past changes and will survive any future climate change except perhaps resulting from a large impact or our sun growing into a Red Giant.

Her face fell though when I said, we weren't concerned about the planet as much as we were concerned with the animals and even the human beings on the planet. I am amazed that we must still argue over the presence of climate change here on earth. I guess I'll just keep taking my show on the road one classroom at a time.

I bet the dinner discussion that night was interesting.

The traveling meme

I caught this over at Looking for Detachment and thought I would add my two cents. I love traveling and seeing different places around the world..or at least different places of my part of the world.

The year started skiing on Red Mountain Pass. The winter ended with "normal" snowfall and good water all summer.

The big trip was flying to San Francisco for the birth of our first grand child. It is so much fun watching your kid being a parent!
I spent some time outside the Colorado Plateau in Ladore Canyon last summer. We followed the Green River down from Flaming Gorge dam all the way through Dinosaur NM. Some fun geology!
The Green River
Riding bikes in the Circle Cliffs of Utah
I took a couple of trips to DC. One working with NG who keeps us busy every second we are there.
We have always been interested in the ruins and rock art we see as we look at geology across the plateau. This summer we started getting serious about studying archeology. Here we are on a back country hike in Mesa Verde
The Colorado high country!
This fall I spent a lot of time in and around Moab. Whether it was bike riding, canyoneering or geology field trips, I learned more about the area this year than in many other field seasons.
We even caught a flash flood.



..and now it is winter again. Another full season of exploring the 4-Corners area.

Here is the Black Canyon
and the Red Mountain mining district.
We were able to catch one more riding weekend in Moab. Riding towards the La Sal mountains
No, I didn't crash. I just wanted my bike in the picture right below "the tombstone" a Wingate monolith.

What is in a name?

I am a bit slow on the uptake sometimes. It took me awhile to regularly use the Neogene and the Paleogene instead of the Tertiary period. I am dreading the day when the Quaternary will no longer exist. But last month while in the Canyonlands I noticed that one of my favorite formations apparently does not exist. No its not some revisionist erosion but a change in naming.

Elephant Canyon is a really fun little canyon deep in the Needles. The canyon bottom has miles of a classic grey/ greenish grey limestone that is full of obvious Permian fossils. It was always a joy to walk the length of the canyon right on the bedding plane between the limestone below and the Cedar Mesa sandstone above. The problem was that the mappable unit called Elephant Canyon Limestone is just not that easy to determine, so for years maps have shown that the Elephant Canyon was inter-fingered with the Halgaito Formation. But now, I see that the Halgaito formation is inter-fingered with the Lower Cutler.

To make the area a little more complicated, just a little bit to the west, the whole sequence of rock units is lumped into the Culter-undivided. Who thought up this system?

Not only does this give me a great excuse to do more research in my favorite place in the world, but I have to learn a new naming system. As any teacher will tell you, I have only so much room for names and that was filled way back in the mid-90's, so wish me luck.

The old stratigraphic column. Taken from the NPS web site. Notice down in the Permian that the Elephant Canyon is listed with the Halgaito Fm. You may have to click to expand.

The new stratigraphic column in miniature font. Please click it to read! Again, down in the Permian the Halgaito shale is now interfingered with the Lower Cutler.