Category Archives: Geology

Eolian Deposition

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Loess Caves in China

While studying a geography unit in grade school I was fascinated by the extensive deposits of loess in China.  Loess is fine wind-deposited soil.  In China, the loess covers a huge area in central China and is an important agricultural region.  The soil is fertile, easy to work, and when it erodes it can form steep cliffs.  People have carved homes into the cliffs for centuries, long enough to be included in geography books in western Colorado.  I lived in western Colorado cliff country, probably responsible for my interest in loess.

Loess is eolian soil, meaning it is wind deposited.  There is also wind deposited sand.  The Colorado National Monument, across the Colorado River from Fruita where I grew up has lots of eolian sandstone.  The cliff forming Wingate and the arch forming Entrada Sandstone are ancient sand dunes turned to stone.  My fascination for wind deposited cliffs comes naturally.

I now live east of the Rocky Mountains.  The mountains are tall and rugged, but are in the process of wearing away.  The Rockies have had several glacial periods.  Glaciers form, grind the mountains, then melt and leave their grinding as sand, silt, and gravel called glacial till. The more coarse debris often was carried in huge quantities onto the plains.  The  smaller particles, sand and silt, were blown onto the plains east of the eroding mountains.

The sand has created extensive sand hills on much of the plains in Colorado.  The sandy soil is thin and fragile, poor for farming, but fine for livestock grazing.  Interspersed among the sand hills are loess deposits now farmed extensively with water drawn from the Ogallala Aquifer in the Ogallala Sandstone, which was washed out of the mountains as the glaciers melted. The Ogallala extends from the mountains into Nebraska and south into the Texas Panhandle.

You may be aware the wind blows in Wyoming.  The entire atmosphere passes through Wyoming in any 24 hour period.  You have seen the Wyoming Wind Gauge?  It’s a logging chain hanging from a post.  I may exaggerate here, but not much.

While blowing, wind carries sand eastward out of the mountains. It also erodes the prairies in eastern Wyoming.  The sand ends up in the Western Nebraska Sand Hill country, covering over a quarter of the state.  The silt blew farther east, building loess deposits along the rivers.

In the dust bowl years in southeastern Colorado, northeastern New Mexico, southern Kansas, and the Texas and Oklahoma panhandles, the dust storms sent silt as far as Washington D.C.  Wind blown stuff is a big deal everywhere.  In North Africa, the sandy deserts are getting sandier as the silt is picked up and blows across the Atlantic Ocean, fertilizing the Amazon Basin.

In Denver, a car sitting outside for several days acquires a significant coat of wind blown dirt.  A couple of years ago, the dirt was red, meaning it originated in eastern Utah.   I notice my sidewalk is lower than the lawn by a couple of inches.  How much of it is organic accumulation and how much is eolian silt and sand?

I went for a long time thinking water is responsible for most of erosion.  It may be true, but don’t discount the wind, especially in Wyoming.

Posted in Eolian deposits, Geology, Rocky Mountains, Sand Hills, Stories, Wind

The Urban Oil Field

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Oil and Gas Wells in Part of Weld County

Weld County, Colorado is one of the richest agricultural counties in the nation.  It is also rich in oil and gas, leading to hundreds of wells extracting petroleum.  With all that money around, Northern Colorado is booming, with people moving and subdivisions being built on what was farmland.  The houses and wells are often neighbors, close neighbors.  As oil companies put profit ahead of proper well management, disasters ensue.  Colorado has lots of fires in the urban-wild land interface.  In Weld County it is the urban-oil field interface.

Colorado is home to 48,000 active wells and 52,000 abandoned wells.  All of them are potential  fire and explosion hazards, and can release methane into the atmosphere.  Think about that when your furnace comes on in the morning before you head out to your car.  We need renewal energy.

The Denver Basin is a huge geologic feature extending along the eastern front of the Rocky Mountains.  As the Rockies were uplifted, the Denver Basin subsided while filling with debris washing out of the mountains.  There is a 22,000 feet difference between the bottom of the Basin and the summits of the mountains.  That is a lot of gravel.

When there is a lot of structure in geologic formations, there is opportunity for oil and gas to migrate into the rocks.  The Denver Basin is one of the largest gas fields in the United States.  Oil and gas extraction started in 1901 in Boulder County.   Trillions of cubic feet of gas and millions of gallons of oil have come out of the ground since then.  Most of the production has come from sandstone or fractured shale.  The development of horizontal drilling and fracking has accelerated the process.  In Weld County, sites with as many as five wellheads and the installations to process the gas are next to residential areas.

Oil Fire Near Homes

The result is spectacular explosions and fires near where people live.  Local fire departments, once used to fighting grass and barn fires, have sprayed thousands of gallons of firefighting foam on the fires and spent days on the fire scenes.  Attempts to increase regulation of the industry mostly fail due to the political clout of the oil and gas industry.  The politics may change with the election of Democrats to most of the state offices.

Keep in mind the oil bonanza is a major source of Colorado’s economy and growth.  The move to renewables is also a source of revenue to the region, but there will be inevitable disruption during the transition.  The oil and gas industry seems to be focused on keeping the wells flowing, regardless of the environmental consequences.  They do not seem to be shifting into renewals themselves, which may be a death knell.  Market forces will probably prove to accelerate the shift to renewables.  They are much cheaper than dragging fossil fuels out of the ground and pouring tremendous amounts of carbon into the atmosphere.  The remains of dinosaurs and ancient swamps need to stay in the ground.

Posted in Colorado, Denver Basin, Energy Policy, Environment, Fire, Geology, Oil and Gas Policy, Stories

Kilauea

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Kilauea

We are living in a momentous time.  The island of Hawai’i is growing.  The entire island is volcanic.  The northern portion of the island is dormant, the south is more active.  It is called the big island, appropriate as it is still growing.  The current eruption started sending lava into the ocean on May 22 and continues as of this writing, August 3.

It seems volcanos are popular places to settle.  Worldwide, people are killed or forced to leave as the earth starts emitting hot stuff near their homes.  Kilauea has forced more than 2000 evacuations.  When Mt. Pinatubo in the Philippines erupted in 1991, more than 60,000 people had to leave.  Fortunately, they had some warning which saved many lives.

It is a mystery to me why development was allowed on Kilauea where lava covered the land as recently as 1960.  Yes, people have property rights, but government has the power to zone property.  It rains a lot in Hawaii, and volcanic soil is fertile, so evidence of lava flow is quickly obscured.

I enjoy looking at the daily USGS reports and maps.  The flows go where they will, without any discernible pattern.  For a week a boat ramp becomes more vulnerable to the encroaching lava, then more lava decides to enter the ocean nearby.  It also seems strange the lava travels so far from the rift before spreading.  The channel from the rift is well established and the levees on either side are growing. The channel is rising and I expect breakouts much closer to the rift, but nothing seems to happen.  I just looked at yesterday’s map.  Lava has broken out upstream from the ocean entry.  I feel vindicated.

Asks usual, government agencies insist on limiting access to the lava flows.  Yes, I understand many people will put themselves in harm’s way and need rescue, but here in Colorado people regularly kill themselves in the mountains and access is allowed.  I would love to put on my heavy boots and look down on a lava stream.   As it is, I read online accounts of people sneaking into closed areas to look at a volcano at work.


Caldera Eruption

The crater is another phenomenon worth seeing.  Before this eruption the lava lake in the crater fluctuated in elevation due to varying supply from the magma reservoir below.  Once the fissures opened some distance from the caldera the lava lake began dropping.  The amount of lava now flowing down the channel exceeds the supply that was in the crater.  Thus, magma is flowing up from the deep.  The Hawaiian Hotspot is alive and well and the archipelago continues to grow.  Pele is not at all concerned about people scurrying around on her rocks.

Posted in Eruption, Geology, Kilauea, Stories

El Volcan De Fuego

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Fuego

I no more than post about Kileaua, a shield volcano, when Fuego, a stratovolcano, lets loose.  Guatemala is part of a string of beautiful Central American countries harboring many volcanos.

 

 

 

The Cocos tectonic plate is smashing into the North American Plate just north of the Caribbean Plate.  As the Cocos dives below the North American, its rock containing lots of water goes down (subducts) and is heated by the hot magma in the mantle.

 

 

 

Pyroclastic Flow

New, lighter magma is formed which then rises and erupts.  The volcano’s lava doesn’t just flow out as in Hawaii.  Stratovolcano magma is more viscous, sticks and plugs the magma channel until pressure builds up and it blows in an explosive, destructive eruption.  The hot stuff rises into the atmosphere (ash), and also flows down the mountain as a  pyroclastic flow of superheated rock and ash, the killer.  Pinatubo in the Philippines, Pompeii, Etna, Mt. St.Helens,

Rainier, Lassen, Hood, and El Volcan de Fuego (Fuego=Fire).  The volcanos ring most continents and island arcs.

Kileaua has been erupting for a month with just a few injuries, and Fuego has probably killed hundreds in one day.  Don’t live too close to a stratovolcano.

Posted in Geology, Stories, Volcanos

Pele

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Kilauea

Pele is the Hawaiian Volcano Goddess.  Like many goddesses, she is both creator and destroyer.  She built the entire island chain, is now busy making the Big Island bigger, and is working on a new one that is just a seamount today.  It’s interesting most everyone in Hawaii believes in her and are resigned to her moods.

She is really in a mood now, both building and destroying.  If you haven’t been following the eruption, go to the USGS website or Facebook feed and watch.  We have a unique opportunity to watch new land being created.  Broadly there are two main types of volcanos – shield volcanos like Kilauea, and stratovolcanos like the ones on our west coast.  Mt. St. Helens is the latest example of what stratovolcanos can do if they have a mind to.

There are some minor ones, but those are the big two.  Their difference stems from the magma rising from the interface of the crust and the mantle.  Two types of magma create volcanos.  Stratovolcanos have felsic magma, derived from the lighter crust beneath continents.  The most common felsic rock is granite.  Shield volcanos are made of basalt, a mafic rock making the ocean floor.

Mt. Rainier

Stratovolcanos tend to form those big conical mountains people like to view or climb.  All the Cascades are stratovolcanos, Mt. Rainier being the most famous.  Felsic magma is less viscous and as it rises from the magma chamber the gasses are trapped until the pressure exceeds the pressure of the overlying rock.  Then it blows.  When Mt. Hood blows, goodbye to Eugene.  When Rainier blows, goodbye Seattle and Tacoma.

Mafic magma is more dense and less viscous and tends to flow out and spread with less violence if you can call a 300 foot high plume of 2000 degree lava less violent.  All that black lava spreading over the land is violent, it’s just not as explosive.  It’s gas bubbles that cause explosions.  As magma rises, there is less pressure, allowing gas bubbles to expand and some water becomes gas.  If the bubbles can move through cracks and voids in the magma it rises to the surface without big explosions.  If the magma is more homogeneous, the gas stays in place until its pressure exceeds the weight of the overlying magma and things go boom.

Shield Volcano

We are on a big ball of stuff.  The core tends to be iron, but there are radioactive elements there and when they decay, they give off heat.  So, we are living on a ball of really hot stuff, made of layers with different density.  Felsic rock continents are less dense than the mafic stuff under them.  They float on mafic magma much like an iceberg in the sea.  Most of the continent’s mass sits down in the mafic magma.  You can’t call deep magma liquid, it is more plastic, but it moves.  Hotter stuff rises through the cooler stuff above and sometimes makes it all the way.

It can rise into the mid ocean ridges, ooze out and spread.  A tectonic plate is forming.  As it moves away from the ridge, it runs into the lighter continent and heads back down, but not without making a mess on the continent.  There is the origin of stratovolcanos.  Mountain ranges and volcanos are mostly on the coasts.

Pacific Ocean Island Chain. Progress of the Hotspot

There are other place where magma surfaces called hot spots.  A plume of magma rises from the deep, belching and vomiting as it gets to the surface.  Hawaii, Iceland, and Yellowstone are hot spots.  The Hawaiian hot spot is out there in the Pacific where mafic magma lives, so shield volcanos form.  Lava flowing created the islands.  Yellowstone is in felsic rock country on a continent so periodically it blows up.  Really blows up, laying waste to hundreds of square miles.  If it happens, Denver is toast.

Tectonic plates move over the hot spots, leaving a chain of Hawaiian islands.  The Yellowstone hot spot has left a trail across Idaho.  Much of that track is composed of mafic magma that found its way up as the continent travelled west.  Lots of basalt there, forming the Snake River Gorge.

Don’t expect all this planetary action to slow down anytime soon.  There are still radioactive elements decaying and the rock doesn’t cool off very fast.  We have to resign ourselves to living on a big stirred up rock that will shove things around and pump magma out on the ground.  Thus, we must give Pele her due.  She is our neighbor and will do what she will.

Posted in Geology, hawaii, Stories, Volcanos

The Enigma of the Colorado Plateau

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Although I have lived somewhere along Front Range Colorado most of my life, I still think of the Colorado Plateau as home.  I am dedicated to the region because of its Geology.  All that rock is just sitting there looking at you.  There aren’t too many plants to get in the way.  I grew up looking at the red rock of the Colorado National Monument just across the river from home.

Thing is, the red rock is mostly from the Mesozoic.  There is a lot of boring buff colored rock from the Cenozoic, notably the Green River Formation.  The Green River Isn’t much to look at, but it has a huge present day impact.  Look at my piece on the Formation in Categories.

I am currently interested in the time after the Green River Formation was deposited.  The literature on this time on the Plateau is relatively sparse, mostly because it was more a time of erosion, not deposition.  A large part of the deposition was in fresh water lakes with only remnants of the sediments today.  Those red rocks forming canyons and arches get all the press.

For most of its existence, the Colorado Plateau had no outlet to the sea.  Then, a bit less than six million years ago. The Colorado River decided to head for  Baja California.  There have been lots of explanations for this happening, but they boil down to elevation change.  The Plateau ended up higher than the Basin and Range province to the west.  That area was once a highland, but big tectonic forces changed everything. Then, a stream eroding east carved enough of a canyon to capture the Colorado Plateau drainage which became the Colorado River.

As you are aware, the Pacific Plate is colliding with the North American plate.  The collision is not at right angles, the Pacific Plate is headed northeast.  As it slides along, it pulls on the North American plate, somewhat pulling it apart.  The area east of the Sierras known as the Basin and Range is being stretched.  As it stretches, big blocks called grabens drop down, leaving mountain ranges between them.  The area ended up lower than the Colorado Plateau.

The Basin and Range Stretched

It’s not entirely clear if The Plateau was uplifted during this time by remnants of the same forces responsible for creating the Rocky Mountains.  It seems to me the uplift was earlier, but my reading on the issue is not conclusive. The fact is the Plateau ended up higher than the Basin and Range.  Erosion then began digging away in the area west of Grand Canyon, hooking up with the internal drainage of the Plateau.  Canyon cutting began.

All those spectacular canyons are younger than six million years.  An interesting sidelight is that the stretching of the Basin and Range continues, and the Colorado Plateau is slowly rotating clockwise.  The question for me is why is the Plateau still in one piece?  Compression, stretching, rising magma, new mountains, collapsing Nevada, huge volcanic fields, Arizona mountains wearing away, all this stuff going on all over the neighborhood, but this one slab mostly stays in one piece. Why?

My personal hypothesis is, as the Plateau houses the Center of  the Universe, it necessarily stays in one piece.  I haven’t found anything in the literature to support this, so we will look at some other explanations.  By the way, the Center of the Universe is within a 100 mile radius from the confluence of the Green and the Colorado.  Let me know if you find it.

In the meantime we will see what the geologists have to say.  Usually they reach some consensus, except here.

If you want to explore all this on your own: Carving Grand Canyon, by Wayne Ranney and Geological Evolution of the Colorado Plateau of Western Colorado and Eastern Utah… by Robert Fillmore.

Posted in Basin and Range, Canyonlands, Colorado Plateau, Colorado River, Geology, Grand Canyon, Green River Formation, Plate Tectonics, Stories

Kodel’s Canyon

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Geologic Time Scale

Growing up in Fruita, Colorado on Colorado’s Western Slope I had rich opportunities for exploration.  The area is amazingly diverse, offering the 10,000 foot elevation Grand Mesa to the east, the stark Bookcliffs to the north, and the spectacular red rock canyons of the Colorado National Monument just south of town.  All this surrounds the Grand Valley where I grew up. These areas and others were within short driving distance, with the Monument in bicycle range just across the Colorado River.

My friends and I used to take our .22s across the river and assault hundreds of rocks.  Our wandering took us across the National Monument boundary into Kodel’s Canyon.  Nobody went there in those days so we didn’t worry about having illegal guns in the park.  The canyon was smaller than the others, but we had the place to ourselves.  The approach is a deeply eroded plain of Dakota Sandstone from the river to the canyon.  The Cretaceous Dakota grades off to the Mancos Shale of the Grand Valley floor.

Kodel’s Canyon

That Mancos Shale is usually called Stinking Desert by many.  It is somewhat infertile unless well drained, and results in mostly barren gray flats.  Lots of barren gray flats from central Utah to Delta, Colorado.  With water and good drainage to carry the salt away, it can be farmland.  We would leave home on the valley floor and climb into the red rock Kodel’s Canyon.  At the mouth of the Canyon is the Kodel’s Canyon fault, where the Uncompahgre Uplift shoved all those Older Jurassic red rocks above the Cretaceous Valley.

Looking at the Grand Valley from Colorado National Monument

The bottom of the canyon is smooth rounded granite and schist geologists call basement rocks.  They are seldom found exposed on the Colorado Plateau, covered by thousands of feet of sedimentary rocks.  The time gap between those old basement rocks and the sedimentary rocks sitting on them is over a billion years.  It’s called the Great Unconformity, where all the rocks deposited during that billion years were eroded away.  This gap is found in many places worldwide, but there are also many places where the rocks missing in our canyon were deposited and remain to be seen and enjoy.  Think the Flatirons, Red Rocks, and the Garden of the Gods, all Cambrian.  Those rocks sit on Precambrian Gneiss and Schist 1.7 billion years old.

Those old rounded black rocks are great for climbing and we did it.  Today it’s called bouldering.  We didn’t have climbing ropes, so we used our .22s as climbing aids.  Dangerous?  Yes. Fun? You bet.

Among the guys I grew up with, only one had any injury running around across the river.  Jerry had a seriously sprained ankle.  The two guys with him helped him down to the road and help.  He exploited the ankle to excess.  At Boy Scouts we always played Capture the Flag after the meeting.  Jerry would hobble down to get the flag defying anyone to stop him.  I walked over and pushed him down.  I don’t think he ever forgave me.

Posted in Colorado National Monument, Fruita, Geologic Time, Geology, Gold Mining, Great Unconformity, Guns, Hiking, Kodel's Canyon, Memoirs, My Story, Rock Climbing, Stories, Uncompahgre Uplift

Plate Tectonics

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Western Colorado’s Grand Valley

As a Western Colorado Native, having lots of geology looking down on me sparked my interest in the field.  I have to know, so knowing how the Bookcliffs, Grand Mesa, and the Colorado National Monument got there stirred my curiosity.  Plate Tectonics is responsible for that stuff poking up all over the place.

Back in the Permian when I took geology at Mesa College, the orthodox explanation for mountain building was something called isostasy.  Push down in one place, and something will pop up nearby.  New Orleans and the Mississippi Delta is sinking under the weight of all that mud coming down the river.  New England is rising a little because that heavy glacial ice sheet melted.  Geologist tried to make isostasy work in places like California with little success.

The early twentieth century saw some new thinking.  Alfred Wegener proposed that continents move around on our sphere.  He was laughed at when he gave papers on the idea.  Yes, Africa and South America look like they once fit together, but how can an entire continent move?  That is a lot of mass to be sliding around.

In the nineteen sixties new thinking started to change attitudes.  Why are there identical fossils on the African and South American coasts?  The real game changer came when oceanic exploration found the mid-oceanic ridges with young basalt near the ridges and steadily getting older farther away.  The only explanation was a spreading seafloor.  Things are on the move.

After college I subscribed to Scientific American magazine.  It seemed like a new article appeared every month explaining how physical features are the result of magma (molten or hot and plastic rock) on the move.  There are seven big (North America, Asia) plates and a number of smaller ones being affected by the rock coming from that spreading seafloor.

Subduction

As the oceanic sea floor impacts the boundary of a continent, something has to give.  The more dense seafloor basalt tends to dive under the continent.  They can form trenches almost seven miles deep next to a subduction zone where the plate dives under the lighter rock of a continent.  The subducting rock is wet, and changes chemically forming lighter rock that often belches up as volcanos.  Earthquakes occur as the plates bump against one another, dip, or slide.

The island arcs off Asia are the current example.  Java, the Philippines, Japan, New Guinea are all volcanic islands getting ready to smash into Asia.  India already has, creating the Himalayas at the suture.  Lots of shaking there, too.

Around 1.75 billion years an island arc docked (yes, geologists use that word) on the Wyoming Craton.  The craton has some rocks as old as six billion (abbreviated as 6 ga) years old.  Many of the rocks are around 3 ga.  The oldest Colorado rocks are around 1.75 ga.  Just outside Morrison, Colorado is the Great Unconformity.  The red rocks are about 60 ma (million years).  The dark gneiss and schist just barely up Bear Creek canyon are those 1.75 ga guys.  Lots went on between those dates, but there it is all eroded away.

Snowy Range, formed by Colorado smashing into Wyoming

The Snowy Range in Wyoming is a result of the join-up.  The coastal ranges in California that like to shake and burn and belch fire and rock formed from the collision of the Pacific and North American plates.  As you are probably aware, L.A. is headed for Anchorage.  Don’t worry it’s going to take a while.

The Rocky Mountains are kind of a strange story.  Usually mountain building occurs at plate boundaries, like the Andes and the Cascades.  What is known as the Laramide Orogeny that created the Rockies happened about 800 miles inland.  The idea is that for some reason about 80 ma the pacific plate scooted under the lighter continental rocks before diving. The Rockies came up a bunch, the Colorado Plateau, my homeland, not so much.

The Rockies are now sitting still but the plateau is moving clockwise, pulled by the pacific plate sliding north against and under the north american plate at the continental boundary, as things should happen.  The Basin and Range province, Nevada mostly, is being pulled apart.  For some reason the Colorado Plateau wants to stay in one piece while western Utah, Arizona, and Nevada are coming apart.

All this motion is happening at about the rate your fingernails are growing.  It doesn’t seem like much, but after a few million years we are talking big moves.  Stay tuned.

My favorite book on these topics is Annals of the Former World, by John McPhee.  It is a big book composed of sections covering the territories along I-80.  Great reading.

Posted in Colorado Plateau, Earthquakes, Geology, Golden Fault, Plate Tectonics, Stories, Utah, volcanoes, Yellowstone Volcano

Weird Wyoming

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Along with having the entire atmosphere pass through the state in any 24 hour period, Wyoming has some other attributes beside the wind.  I like Wyoming for its diversity and the fact it doesn’t have too many people.  The diversity also extends to the geology. Prairie in the east, Devil’s Tower and the beautiful country around there to some of the most spectacular alpine country anywhere, even if the mountains are lower than ours in Colorado.  Oh, and Yellowstone, our first National Park.

Wyoming Geology

I especially like the deserts, like the Great Divide Basin, aka the Red Desert, a depression rimmed by the Continental Divide.   Yellowstone is the largest and most dangerous volcano in the country.  There is coal, iron ore, oil and gas, uranium, and trona, to name a few.  Those resources are a double edged sword, leading to a boom and bust economy.  Ranching just soldiers along,  but it is a hard way to make a living.

A good portion of the economy comes from Greens (Coloradans, known for their green license plates).  It’s the topography that draws me.  Rivers flowing north, through mountain ranges, fed by hot springs.  A range of hills known as the gas hills, where methane comes out of the ground.  Mountain ranges running north and south as God intended, but the Snowy Range runs east-west and is the boundary between the ancient island arcs known as Colorado and the much more ancient Wyoming Craton.

The Wyoming Craton has some of the oldest rocks in North America, sharing the antiquity with the Canadian Shield.  Ages vary but are around 2.6 to 2.8 billion years old.  The oldest rocks in Colorado are around 1.7 billion years old and arrived as an island arc smashing into Wyoming, much as Indonesia and the Philippines are headed to Asia.

Wyoming has had a lot of activity down deep, shoving mountains up and sliding them around.  That pushing and shoving means areas where oil and gas get concentrated in the bends and corners, thus all the oil patch work there.  There is a lot of coal. The Union Pacific got its coal right near the tracks, and there is a tremendous amount of coal in the Powder River basin.  Coal is out of favor now, so Gillette is hurting, people leaving.

The reason Wyoming got famous is for two reasons, unruly Indians and the livestock business.  There was a lot of Indian fighting in the middle of the nineteenth century, what with the Oregon Trail crossing the region.  When the Indians were whipped, all that empty country became home to cattle and sheep.  The livestock people still hold most of the political power – they also have oil and gas leases, so they aren’t very environment friendly.  Lots of cowboy legends came out of the place.

My favorite things are the rivers running through mountain ranges.  The textbook example are the Wind and Bighorn rivers.  They got their names because early explorers didn’t realize they are the same stream bisected by the Hot Springs Mountains.  The Bighorn flows south through Thermopolis and its hot springs and roses into a beautiful narrow canyon.  The Wind River flows out of the canyon.  The river was there, the mountains came up, and the river (rivers?) stayed in the same place, cutting the canyon as the uplift occurred.

Do I need to say the Wind River is aptly named?  Years ago in Colorado Springs I met a bicyclist doing a ride across the country.  He came across Wyoming.  He looked at me and in awe said,  “The Wind”.  He rode into the wind all across the state.  Another time I was driving from Laramie to Fort Collins after dark. It was Christmas time and the ground blizzard was in full song. I saw a VW bus along the road near Tie Siding. In conditions like that, you stop.  The occupant was from Australia and said “I’ve never encountered weather like this.”  It was around zero with 50 mph wind.  The VW had quit, probably a frozen gas line, and his wife got a ride into town to get help.  Shock and awe.  I just laughed and saw he was OK.  You know about the Wyoming Wind Gauge.  It’s a length of heavy chain hanging from a post.

Jackalope,, Wyoming State Animal

There is usually a Jackalope colony nearby.

There are three books I recommend:

Rising From the Plains, John McPhee; Roadside Guide to Wyoming Geology; and Wyoming Geologic Highway Map

Posted in Coal, Geology, Green River Formation, John McPhee, Stories, Volcanos, Wyoming, Yellowstone Volcano

Denver Basin

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Denver Basin

The Denver Basin is a deep syncline just east of the Southern Rocky Mountains.  It started around 300 million years ago when the Ancestral Rocky Mountains were uplifted.  A little plate tectonics here, folks.  A tectonic plate is a huge plate of rock slowly moving on the earth’s mantle at or near the surface. When two tectonic plates collide, one of them often dives beneath the other.  As the plate subsides, it runs into hotter rocks at depth.  The subsiding plate has lots of water which lowers the melting point of the rock.  Then things really go on the move.

The subsidence zone, usually along a coastline, gets pretty active, meaning earthquakes, volcanos, and the intrusion of huge blobs of granite known as plutons.  New rock coming in from below means the overlying rocks get uplifted into mountain ranges.  The other side of this mountain building is known as the foreland and usually subsides as its mass goes into the new mountains.  As it subsides, the new basin fills with debris eroding from the mountains.

The Flatirons, Dakota Ridge, the Garden of the Gods, all are built from rocks buried thousands of feet deep just a few miles from the outcrops.  I am sitting here writing atop thousands of feet of mountain debris.

The mountains eventually get hauled away in rivers or dumped into the basin.  This happened twice here in my home country.  The second event occurred at the end of the Cretaceous and the early Paleogene, about 60 million years ago.  Our current Rockies came up, known as the Laramide Orogeny, came up again, and the foreland deepened even more.  It ended up being about 13000 feet deep, filled with the stuff washed and blown off the mountains.

This all took a while.  Rivers formed, seas came and went, and lots of life contributed organic material to the basin.  The result?  Coal, oil, and gas.  The first oil well was in Boulder County, producing from fractured Pierre Shale, which was deposited by an inland sea.  Now this Basin is big, extending into Nebraska and Wyoming.  Huge amounts of oil and gas have been produced, and horizontal drilling and fracking are releasing even more.  The Denver Basin is an oil patch.

Water from the mountains also entered the basin, creating aquifers producing lots of water.  We pump the water and because it is in an enclosed basin, it doesn’t recharge as fast as it is pumped.  Douglas County is going to run out of groundwater some day.  Then the water will have to come from the rivers, and the supply is limited.  Thus, seemingly crazy proposals to pump water from Flaming Gorge Reservoir on the Green River in northern Utah to Eastern Colorado.  Problem: California and Arizona also want that water.

Climate change has the potential of reducing the available water as well, eventually ending population growth.  Amazon, Stay Away.  Mining started Colorado development, and today the money still comes from the ground, but is from oil and gas. As we transition to alternate energy sources, where is Colorado’s wealth going to come from?

Posted in Colorado, Colorado Mountains, Denver Basin, Geology, Golden Fault, Oil and Gas Policy, Stories, Subsidence
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