Friday, October 31, 2014

On the Road: Final Geo-challenge

Where am I?  what's all that weird orange rock?!  maybe I was out too long.
Plants and Rocks is back from vacation, with one more geo-challenge to share.  But I had to wait until today to post it (hint).
It was a land of strange and eerie rock creatures – hundreds of them!
Those in the prime of life were spooky ...
... but the old and dying evoked sympathy.  Though made of rock, their lives are short.
Where on Google Earth? Click on image to see hordes of rock creatures southeast of parking lot.

video
(music – Ghosts in the Kitchen, © Poorpersons Enterprises 2003)

Monday, October 27, 2014

On the Road: Geo-challenge 2

Where are we now?  View is from behind, as the sun sets.
Plants & Rocks is still on on the road and finding it hard to blog, so here’s another quick geo-challenge.  The first was the geologically very cool Uinta uplift; more on that later.  Then I visited another Laramide range.  This one has an unmistakable east flank – too easy for a geo-challenge.  Instead, here are views “from behind”.
Sandstone cliffs in evening light with a laccolith in the distance.
Another laccolith on the right horizon – in fact the type locality.
Morning view.  The large mesa to the southwest is capped with volcanic rocks.
In the “high country”.  No Precambrian rock is exposed, and the vegetation is piñon-juniper woodland.

Wednesday, October 22, 2014

On the Road: Geo-challenge 1

Where are we?

Plants & Rocks is on vacation.  First destination was an east-west mountain range often described as an anomaly because contemporaneous ranges mostly trend southeast-northwest.  Actually there are several others like it, though not as large.  This one may have been influenced on the north by the Cheyenne Belt -- an east-west suture zone where crust was accreted to ancient North America roughly 1.5 billion years ago.
Red sedimentary beds on left are Precambrian.  They fooled all three early geological explorers.
The Precambrian core of the range is sedimentary – conglomerate, sandstone, siltstone and shale.  Sediments were deposited in a rift valley when the continent was coming apart, close to where it had been sutured.  It didn’t tear all the way, but was deep enough to accumulate 20,000+ feet of material.
Something like seven hundred million years later, the east-west mountains rose during a great regional mountain-building event (below).
Sedimentary strata on the flanks of the uplift were steeply folded, making for great scenery.  Some roads follow strike valleys between spectacular hogbacks.
The sedimentary rocks are just as wonderful on the south side of the mountains – like the ones below.
Josie Bassett ranched here at the mouth of the box canyon until she was 89.  “Independent in both action and thought, she lived life on her own terms.”

Sunday, October 12, 2014

Walking the Devil’s Backbone

Driving home from Rocky Mountain National Park we stopped just a few miles west of Loveland, Colorado, to examine the Devil’s Backbone.  How could we not?!  It’s an eye-catching landform and there’s a trailhead at the south end, right off Highway 34.

Demonic geologic features are common in Colorado -- there are at least twenty-one (Colorado Geological Society 2009).  Curiously, all are composed of either igneous rock or Mesozoic sandstone (Mesozoic means 252-66 million years old).  Some early geologists assumed the Devil's Backbone was igneous, a dike.  It has that look -- long, linear and narrow.  But then someone investigated and found it’s Mesozoic sandstone, specifically the Dakota sandstone -- sediments deposited by rivers flowing into an interior seaway to the east roughly 100 million years ago.
Here the Dakota is a mix of fine and coarse river deposits.  Note nearly vertical orientation of beds.
Along the Front Range of the Rocky Mountains, the Dakota forms hogbacks -- ridges of steeply-tilted sedimentary strata.  In the Devil’s Backbone the sandstone is really steep, basically vertical.  It's part of the west flank of a small anticline (uplift) east of the main Rocky Mountain uplift.  The more gentle east flank of the anticline is visible from the trail.  In the next photo, it's marked by rimrock with trees on the horizon, above boulder-strewn slopes.  The Triassic red Chugwater Formation is exposed in the valley below.  The valley also contains the “crest” of the breached anticline (cut through by erosion.)
Looking from the Backbone toward the hogback on the east flank of the anticline. 
The Wild Loop trail along the Devil’s Backbone is about two miles roundtrip, and is an easy stroll.  A short spur leads to the “Keyhole” where you can stand among the Devil’s vertebrae!
A demonic vertebra.
The Keyhole.
Long's Peak (Rocky Mt NP) from inside the Keyhole; Dave's finger rests on summit (click on image to view).
For more information, download the trail brochure provided by Larimer County’s Parks and Open Spaces.  This is the southern end of a network of trails extending north along the Front Range to Fort Collins.  Consider a weekday visit.  It’s popular, and the parking lot often fills on weekends.

NOTE:  The Devil has multiple backbones -- at least eight in the USA.

Tuesday, October 7, 2014

Tree-following: that first question

Do you remember that first question ... back in February when the cottonwoods were leafless, the ground in snow, and the river under ice?
“Is this a single individual, connected underground?”
Time passed, more questions arose:  What kind of cottonwood? (lanceleaf)  How tall? (58.4 feet)  Male or female? (female).  But the first question was never answered.
Cottonwood at dawn.  Is this a single tree, or six?
Most cottonwoods send up suckers -- shoots from buds on the roots.  Old stumps and even fallen branches sometimes produce shoots that grow to maturity.  So it’s reasonable to suspect that this clump is a single individual.  Most cottonwoods along the Laramie River are clumped like this.
Lanceleaf cottonwoods along the Laramie River in early morning light.  Note bird on wire (more later).
Then a clue appeared.  The east half of the cottonwood tree I'm following is now yellow, the west half still green.  Perhaps this isn’t a single tree after all.  We investigated.
My cottonwood tree(s) -- now green and yellow.
Its canopy.
Glen at base of tree(s).
We crept into the little glen among the trunks.  The sound of pitter-patter footsteps and buzz-like whispers swelled and then quickly subsided -- probably river elves fleeing their sanctuary.  To the east towered three stems (maybe-trees) with yellow leaves.  Two to the south still had green leaves as did the younger one to the northwest, which split just above the ground.
Three stems with yellow leaves (green ones belong to stems on right out-of-sight).
Two stems to the south still sport green leaves, though they're fading.
This younger stem became two at some point.
So how many trees?  Might we say at least two -- the yellow and the green?  Then a vague distant memory from botany-student days surfaced.  Being immobile, plants may resort to phenotypic plasticity and produce different forms from the same inherited DNA.  Besides, I like the whole clump and want to follow it.  Are you wondering how one follows an immobile organism?  Apparently you don’t know of the tree-following frenzy hosted by Lucy Corrander.  Visit this month’s gathering to learn more.
A bird with a distinctive silhouette.
Back to the bird on the wire.  A belted kingfisher has been fishing from this wire across the river just upstream from the footbridge for at least 20 years.  As the EPA says, “No information was found in the literature on life expectancy for this species.”  So every year I wonder:  Is this a single bird, or many?
Sometimes our “intrusions” benefit wildlife -- belted kingfishers love telephone wires near streams and ponds.