Structural geology and mineralogy at Calico

March 16th, 2011

ZZYZX, CALIFORNIA–It was surprisingly cool this morning in Zzyzx as we left for our day of fieldwork, but we were not surprised by the wind at our first stop, Calico Ghost Town outside Barstow. Every time we’ve been there it has been blustery. Calico is an old silver mining site with a complex geological structure complimented by hydrothermal mineralization driven by dacite intrusions roughly 17 million years ago. Shelley Judge showed us how strike-slip faulting (ultimately a result of movement on the San Andreas Fault to the west) produced compressional folds in the Barstow Formation. Meagen Pollock talked about how the silver rich veins were formed by thermal alterations of the sedimentary rocks on the flanks of the Calico Mountains. We then spent a little time in the town itself eating our packed lunches and enjoying cold sarsparilla!

Plunging into Lake Manix

March 15th, 2011

ZZYZX, CALIFORNIA–East of Barstow and west of Afton Canyon was a very large pluvial lake during the Pleistocene. This Lake Manix was hundreds of feet deep, and its catastrophic drainage through Afton Canyon about 185,000 years ago must have been a great spectacle. This afternoon we explored one of the southern shores of this ancient lake, and then climbed down through its eroding bottom sediments.

Shoreline of Pleistocene Lake Manix. The dark rocks to the left apparently are remnants of an alluvial fan delta which extended into the lake shallows. The light-colored sediments below and to the right are from the lake itself. The white band in the foreground appears to be a type of coastal tufa formed by the agitated lake waters mixed with waters coming from the fan.

Lake Manix bottom sediments consisting mostly of fine silts and clays.

The plateau above the lake sediments includes windswept desert pavements and beautiful ventifacts (wind-carved stones) like this one.

A morning with the Barstow Formation

March 15th, 2011

Greg Wiles explores the top of a wadi in Owl Canyon. The debris here consists of blocks of Barstow Formation eroded during recent floods.

ZZYZX, CALIFORNIA–It is hard to believe that the Mojave region once had vast lakes, erupting volcanoes and a diverse mammalian fauna including camels and horses. The most important record of this time is the Barstow Formation (Miocene — about 15 million years ago). This unit contains river and lake sediments along with volcanic ash, all of which produce a diversity of colors leading to the name “Rainbow Basin” for the best exposures outside Barstow, California.

The Wooster geologists spent the morning with the Barstow Formation in Owl Canyon and Rainbow Basin. The highlights included a group analysis of dozens of rock specimens, a desert tortoise crossing the road, and meeting old friends Buzz and Phyllis Sawyer from Barstow.

The Wooster geologists in Rainbow Basin with the Barstow Syncline in the background. Image by Buzz Sawyer.

Death Valley Day

March 14th, 2011

ZZYZX, CALIFORNIA–Our Wooster geological crew awoke to a spectacular sunrise over the Soda Lake playa this morning. We drove north from Zzyzx through Baker and Shoshone into Death Valley by way of Jubilee Pass. The weather could not be better with daytime temperatures in the low 80s and brilliant blue skies. Shelley Judge gave us an overview of the tectonics that formed Death Valley, Meagen Pollock helped us sort out the poikilitic textures in basalts along Artists Drive, Greg Wiles discussed the declining levels of Lake Manly, and I helped out with interpretations of sedimentary structures in Miocene deposits exposed along Golden Canyon. Students kept their end of the bargain with challenging questions. A most excellent day.

Part of Death Valley's charm is in its extremes. This is Telescope Peak on the western side of the valley. It is 11,049 feet above sea level. Note the snow cover.

And here are salt deposits below Telescope Peak at 275 feet below sea level, baking in the relentless sunlight.

The Wooster students on the 2011 Mojave Desert field trip.

Wooster Geologists return to the Mojave Desert

March 13th, 2011

ZZYZX, CALIFORNIA–All four geology faculty members, our administrative coordinator Patrice Reeder, Jesse Wiles and eight students have safely arrived at the Desert Studies Center in the delightful Zzyzx.  We spent a few hours exploring the Jurassic sandstones exposed in the Red Rocks Conservation Area outside Las Vegas (with marvelous dune cross-bedding) and then slogged through horrible Los Angeles-bound traffic from Las Vegas to Baker, California.  (All too typical for a Sunday night here.)

Unfortunately bandwidth is highly restricted, so our posts will be infrequent until we return to Wooster.

Lichen and bits of desert varnish on the cross-bedded sandstone at the Red Rocks National Conservation Area.

Lindsey Bowman apparently saves Becky Alcorn with a dramatic backdrop of cross-bedding.

Experiential Learning in the Desert

March 11th, 2011

As Dr. Wilson so gleefully pointed out today, the last several blog posts have been about fossils. I think it’s about time for a change of subject, don’t you?

Spring break officially begins tomorrow, and this is what Wooster looks like tonight:

A view of the snow covered street from my living room. I had to take the picture tonight because Dr. Wilson would have undoubtedly beat me to it in the morning.

The Wooster Geologists are ready to leave all of the snow behind! In a few short days, we’ll be headed to the warm and sunny Mojave Desert. The Desert Studies Center will serve as our base camp while we explore Death Valley, the Mojave National Preserve, and Barstow, CA (Dr. Wilson’s hometown). We invite you to follow us on our week-long adventure. Be on the lookout for posts that feature blue skies, stunning vistas, and geologists learning about the desert through direct experience. (It’s good to be a geologist.)

The Mojave Desert Field Trip and Wikipedia

March 23rd, 2010

Tertiary debris flow at Resting Spring Pass near Shoshone, California. This is an image from the field trip now posted on Wikipedia.

WOOSTER, OHIO–One of the primary joys of being a geologist is the opportunity to see so many interesting sights in the field.  We can share a bit of the pleasure and advance public knowledge by posting some of our photographs on the free online encyclopedia Wikipedia.  Here are some linked Wikipedia articles which have been improved with public domain images from this month’s Mojave Desert field trip:

Amboy Crater
Aztec Sandstone
Barstow Formation (a new page)
Lake Manly
Calico Ghost Town
Conglomerate
Curtis Howe Springer
Debris Flow
Desert Pavement
Desert Studies Center
Dune
Kelso Dunes
Lake Manix
Lake Tuendae
Mojave River
Pluvial Lake
Red Rock Canyon National Conservation Area
Syncline
Tuff
Volcanic Bomb

Wandering in the wilderness one last time

March 11th, 2010

ZZYZX, CALIFORNIA–This was our last full day in the Mojave Desert, at least for this trip. Technically it was our coldest start yet (40°F), but the bright sun and lack of wind made it seem like our warmest. The day was mostly unstructured because we were going to try to find a geological site none of us had seen here: the lava tubes in the cinder cones area of the Mojave National Preserve. It was a good thing we left our schedule open because we missed not one turn, not two turns, but three crucial turns before we finally entered the tubes. I’ll take full responsibility, although in my defense I must point out that the Preserve is very coy with their signage and directions!

While exploring the desert during our lost phase today, Rob McConnell found this excellent volcanic bomb on one of the cinder cones. Note the streamlines formed as the molten lava cooled as it was thrown into the air. We can even tell which end hit the ground as it landed (the left).

Rob Lydell at the entrance to the lava tube complex in the cinder cones region of the Mojave National Preserve.

Michael Snader, Andrew Retzler and Stephanie Jarvis (looking very straight up!) inside one of the lava tubes with light behind them shining through a hole in the roof.

This light shaft is outlined by eolian dust it is passing through.

After another delicious lunch packed for us by the Desert Studies Center staff (a shout-out to the world-class cook, our friend Eric), we drove north to Resting Springs Pass to study a famous exposure of a welded tuff.  Our last stop was a descent through the 500,000 year-old beds of ancient Lake Tecopa to China Date Ranch where we looked around the oasis and had the famous (and expensive .. and over-rated) “date shakes”. (Think flurry with little date bits thrown in.) The students and other faculty enjoyed them, though, and they were in their eccentric way a fitting end to our Mojave adventure.

Wooster geologists on the welded tuff at Resting Springs Pass.

Adam Samale, Megan Innis, and Rob McConnell sampling the hottest part of the welded tuff series at Resting Springs Pass. (Oh those youthful days of casually perching on cliffsides!)

Andrew Retzler is standing on the down-dropped block on the left side of a fault at Resting Springs Pass, and Stephanie Jarvis is on the upthrown side. What kind of fault is it?

Travis Brown at the front of the store at China Date Ranch near Tecopa, California.

Proof that the date shakes at China Date Ranch were popular. From the top left, clockwise: Andrew Retzler, Micah Risacher, Greg Wiles, Rob McConnell.

Unless my colleagues surprise me this evening, this will be our last post from the Mojave. We will have many more entries for this field trip, though, as we sort through student images and observations back on campus. We will also add more technical notes about the sites we saw, and maybe even throw in a video or two. It has been an extraordinary trip which will live in our departmental memory for a very long time.

Geological diversity: Tuffs, Sands, Limestones and Lava Flows

March 10th, 2010

ZZYZX, CALIFORNIA–One of the most attractive aspects of geology is how many materials and processes are included in the study of the Earth. Today’s field experiences show this diversity. One of the best reasons to teach in a liberal arts geology program is that we are continually in touch with topics outside of our original disciplinary training. This trip has been so much fun in part because all four of our faculty are involved at each of our stops, and we always learn from each other by having no fear about asking any questions. We seem to be successfully modeling this attitude with our students because they certainly have no hesitation in asking questions either.

Our teaching approach in the field has been to introduce students to the general framework of information about a particular site, and then let them explore the area, each bringing back questions, observations and specimens for a summary session with all the faculty. This has worked very well with this class because they are advanced and very enthusiastic students. Their curiosity has been an inspiration.

This morning was sunny, windy and cold (starting in the forties and not getting past 53°F). It hardly mattered though because we had so many interesting outcrops to study.  Our first stop was Hole-In-The-Wall in the southeastern quadrant of Mojave National Preserve. Here are magnificent tuffs from an explosive volcano eruption about 18.5 million years ago. Dr. Pollock will have more to say about the geological details.

An exposed tuff at Hole-In-The-Wall showing "tafoni", which are small cave-like erosion features.

The loop trail around the major tuff exposure involved a steep climb through a slot canyon with the help of embedded rings. It was indeed physically challenging. Dr. Shelley Judge is shown climbing out with skill; Megan Innis points out the warning.

Our second stop was to climb the Kelso Dunes in the southwestern portion of the Preserve. The pile of sand here reaches 160 meters. It is trapped against the Granite Mountains in an endless swirl of winds. The students climbed the highest and most popular dune in the complex while the faculty chose to ascend a slightly lower but untrampled dune. Oddly enough, when we stood on these dunes in the middle afternoon, for the first time the wind stopped!

The graceful top of one dune at Kelso showing the shallower stoss side, steep lee side, and a small sand avalanche.

Dr. Greg Wiles made a trace fossil in the Kelso Dunes to confound future paleontologists.

Our last two stops were relatively brief.  One was at an outcrop of the Chambless Limestone, a Cambrian unit showing oncolites and dolomite-filled burrow systems.  The other was at the tip of a lava flow from the cinder cones near the center of the Preserve.  We returned to the station in the early evening with sand-filled shoes and sun-reddened faces. Another wonderful day in the Mojave.

Micah Risacher looming dramatically over our Cambrian limestone exposure.

Dr. Pollock wanted us to find her a lava tube. We did, albeit a small one, and she seemed happy enough with it.

A most impressive volcano

March 9th, 2010

ZZYZX, CALIFORNIA–Our second and last stop of the day was Amboy Crater, which is about halfway between Barstow and Needles, California, near Route 66. Meagen Pollock, our ace petrologist, prepared us well for this visit, so we’ll wait for her to post the geological details and her expert observations. I want to prepare the ground with some photos of our hike up this remarkably recent cinder cone.

Wooster geologists walking across the lava field to Amboy Crater.

A very happy Meagen Pollock with a volcanic bomb tossed from Amboy Crater.

Wooster geologists on the rim of Amboy Crater trying very hard not to be blown down either the steep slope into the crater or the steeper slope down the outside.

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