Friday, May 22, 2015

Geologic History of Cuba

As the Atlantic Ocean began to open, some 160 million years ago (MYA), the North and South American Plates were forced westward, a tectonic process that continues today.  In concert, the Caribbean Plate was shoved between them.

The geology of Cuba, which lies along the southern edge of the North American Plate, is complex.  It appears that the largest Caribbean island began to form during the Cretaceous Period, some 100 MYA, as collision and subduction volcanism occurred along the margin of the North American and Caribbean Plates, creating a chain of islands.  Since that time, uplift, deposition, erosion, Tertiary volcanism and a prolonged period of submersion (from 35 to 5 MYA) have left behind Cuba's varied topography and geology; rock strata on the island range in age from Precambrian igneous rock (900 million years old) to late Tertiary marine limestone (less than 5 million years old).  During the Eocene Period, some 50 MYA, volcanism occurred in southeastern Cuba (then contiguous with Haiti and the Dominican Republic) forming the Sierra Maestra; then, about 40 MYA, a rift valley began to separate these island nations, shoving Cuba westward.

Today we see the culmination of these geologic processes while understanding that tectonic forces continue to mold our planet, Cuba included.  Indeed, the rift between Cuba and Haiti continues to widen and the American Plates drift westward, scraping past and interacting with the Caribbean Plate (see Caribbean Subduction Zones and Haiti's Earthquake).

Thursday, May 21, 2015

Stressed Swallows

The recent chilly, damp weather in Colorado has curbed the activity of flying insects and has stressed those birds that feed on them.  Swallows are among our most abundant aerial insectivores and their behavior has clearly been altered by the prolonged cold spell.

In recent days I have watched large mixed flocks of barn, cliff, tree and violet-green swallows strafing ponds and meadows in the South Platte Valley, apparently snatching insects that hover near these relatively warm surfaces and gleaning sluggish prey from the grass or water.  The frenzy of activity might also flush insects from the dense vegetation, making them more accessible to the swallows.

One wonders how these birds consume enough prey on such chilly days to balance the energy expended to catch them.  When their aerial efforts prove to been inadequate, swallows are known to snare sluggish insects from bridges, river banks or the walls of barns and other outbuildings.  Nevertheless, the persistent, chilly upslope along the Colorado Front Range is surely stressing these agile hunters.

Wednesday, May 20, 2015

The Nature of Trust

Trust is the sense that another person or human organization has integrity and will act in our best interest.  It is distinct from love and friendship; we place our trust in many who we do not love or befriend and, through the course of our lives, we love some individuals who we cannot trust.

Our ability to trust others is likely affected by our early childhood experience; if we are ignored, abused or abandoned by parents or caretakers, we may find it hard to trust other individuals.  In like manner, repeated episodes of misplaced trust may diminish our capacity to rely on other human beings.  For most of us, over the years, we come to trust a mix of individuals and organizations that earn our respect and rely on them repeatedly for their advice and support; among these are friends and loved ones with whom we share our passions, beliefs, hopes and fears.

Trust is not always permanent.  Some who earn our trust later prove to be deceitful or unreliable; examples are charitable, financial or religious organizations that demonstrate fraudulent activity or engage in behavior that defy their basic tenets.  While our trust in others is frequently tested, we cannot flourish without a willingness to rely on fellow humans and the organizations that foster our passions; in the end, social trust is a vital component of our lives.

Tuesday, May 19, 2015

A Relentless Upslope

Over the past two weeks, a series of Pacific storm systems has produced a nearly continuous period of upslope flow along the Colorado Front Range.  Counterclockwise winds generated by low pressure centers and clockwise flow within atmospheric troughs have directed Gulf of Mexico moisture toward the Rocky Mountain corridor; rising with the terrain, the air cools and condenses, producing overcast skies, chilly temperatures and intermittent rain or snow (depending on elevation).

Indeed, it has felt more like March than May.  Though the greenery is especially lush for this semiarid landscape, the chill has slowed the leafing and flowering process for many trees and shrubs.  Despite flooding along the South Platte and its tributaries, the mountain snowpack has continued to build, threatening even greater runoff when seasonal warming resumes.

In a region renowned for sunny skies and dry air, it's hard to accept such a relentless period of chilly, damp weather.  Though the precipitation will be beneficial in the long run, most of us would prefer the usual pattern of clear, mild days and late afternoon thunderstorms.  After all, Colorado without sunshine just doesn't seem right (unless, of course, it's snowing).

Monday, May 18, 2015

Denver Botanic Gardens Chatfield

Settled by Frank and Elizabeth Hildebrand in 1861 and by the Green Family in 1935, the lower Deer Creek Valley, southwest of Denver, was obtained by the Army Corps of Engineers in 1967 during the construction of Chatfield Reservoir.  Leased by the Denver Botanic Gardens in 1975, the land was first developed as the Chatfield Arboretum, which opened in 1990, and became the Chatfield Nature Area in 2000.  By 2005, a master plan was developed to establish a botanic gardens on the property, highlighting plants native to Colorado while preserving the historic structures and maintaining a working farm.

Accessed from Deer Creek Canyon Road, west of Wadsworth Blvd. and south of C-470, the Denver Botanic Gardens Chatfield is a mosaic of meadows, farm fields, wetlands, gardens and riparian woodlands along Deer Creek.  A network of paved paths, graveled trails and dirt/gravel roads lead the visitor through the varied natural habitats, past the historic structures and along the display gardens.  A day-use fee of $5.00 per vehicle is currently charged for nonmembers.

Birdlife is abundant at the preserve.  Open country species, such as golden eagles, Swainson's hawks, American kestrels, western kingbirds, mourning and collared doves, black-billed magpies, Say's phoebes, western meadowlarks and vesper sparrows, are especially common, while the riparian woodlands attract great horned owls and a wide variety of Piedmont songbirds.  Ponds and wetlands south of Deer Creek host a diversity of waterfowl, shorebirds and wetland songbirds that vary with the seasons.  Mammalian residents include mule deer, coyotes, red fox, muskrats, cottontails, fox squirrels, prairie dogs, raccoons and striped skunks; though black bear and mountain lions may wander down from the foothills, they are primarily nocturnal and rarely encountered.

Saturday, May 16, 2015

The Nature of Avian Flu

Avian flu, commonly known as Bird Flu, is caused by a spectrum of influenza A viruses; many strains and subtypes have been documented and some are highly pathogenic to both wild bird and domestic poultry populations.  While past severe outbreaks of avian influenza have occurred primarily in Asia and Africa, the current North American outbreak (the first since 1983) began in December of 2014.

The spread of avian flu across the Continent is thought to result from infected migrant waterfowl though other regional carriers may be involved.  Once the virus infects individual birds at a poultry farm, it may spread quickly through the closely confined population and, potentially, to other local populations; some strains have been associated with a death rate of 90% or more.  As a result, when evidence of avian flu is documented on a poultry farm, the entire population of chickens, ducks or turkeys is culled and the facility must be disinfected.  The current outbreak is especially severe in Iowa, where more than 25 million chickens have been culled, but local or widespread infection has been documented in 16 States to date; as a result, the price of eggs, poultry meat and egg-containing products is expected to rise significantly.

While human infection from avian flu has occurred in Asia (almost exclusively in those handling infected birds), the current U.S. strains have not demonstrated the capacity to infect humans.  Human to human transmission of avian flu has been very rare but can occur with some strains under special circumstances (direct contact with infected secretions).  Nevertheless, influenza viruses mutate at a high rate and avian flu may threaten human populations in the future.

Friday, May 15, 2015

Country Folk

On our recent trip to Flaming Gorge, my pickup blew out a tire.  Fortunately, we were at the exit for a small town when that random event occurred.

Flagging down a local resident, we learned the name of the town's towing service and placed a call.  The friendly owner arrived within five minutes and towed us to the town's only tire shop; en route, he gave us a brief rundown on his home town, including the opening of a Walmart and the town's second grocery store.  He also recommended a tour of the old, historic prison if time permitted.  Once at the tire shop, we were informed that, unfortunately, repairs might take an hour or more; to bide our time, we were advised to visit a popular coffee shop, run by two older women.  We took that advice and enjoyed both a tasty breakfast and friendly service.  Once back at the tire shop, we caught up on the clerk's family history while awaiting the final repairs.  Ninety minutes after the accident, we were back on the highway and headed for home.

While similar services are available in larger cities, the entire process would have taken most of the day.  More importantly, we would not have enjoyed the personalized service and colorful conversation that came with that small town setting.  Though city dwellers tend to criticize country folk for their provincial attitudes and lack of sophistication, we gain a more accurate picture when happenstance places us in their company.  It is then that we come to appreciate their kindness, skill and genuine hospitality.

Thursday, May 14, 2015

Crossing Southern Wyoming

After leaving the Green River Valley, we drove east on Interstate 80 this morning, headed for our Littleton farm.  Between Rock Springs and Rawlins, Wyoming, we crossed some of the most desolate landscape in the country, covered by a rolling sage grasslands and broken by stark ridges of Cretaceous sandstone.  Lone cows, pronghorns and oil pumps appeared to be the only residents.  For geography buffs, such as myself, there was some reward offered by the topography: we crossed the Continental Divide twice, dipping through the Great Divide Basin.

As we approached Rawlins, a spectacular view of the Bighorn Range unfolded to the northeast and, once past that city, more interesting terrain began to appear.  Far to the south, the Sierra Madre of Colorado poked above the horizon and off to the ENE, Laramie Peak towered above its range.  Further along, we crossed the North Platte River and the massive bulk of Elk Mountain loomed along the south side of the highway, backed by the Snowy Range and more southern sections of the Medicine Bow Mountains.  With plenty of snowmelt from these peaks, the landscape lost its dull, dry appearance and numerous ponds and sloughs lined the Interstate, filled with waterfowl, white pelicans and phalaropes.

Beyond Laramie, we climbed across the broad ridge of the Laramie Range, which offered fabulous views of Rocky Mountain National Park to the south.  Finally, we descended into Cheyenne atop a Gangplank of Tertiary debris and turned south on the vehicle-clogged ribbon of Interstate 25.  We would be home, traffic permitting, in 90 minutes.

Wednesday, May 13, 2015

Flaming Gorge

The Green River of the Western U.S. rises on the northwest flank of the Wind River Range in west-central Wyoming and flows southward through its broad basin of Tertiary and Cretaceous deposits.  Approaching the Utah border, it has sculpted Flaming Gorge, named by Major John Wesley Powell for bright red Triassic rocks that adorn southern portions of the chasm; the scenic gorge now lies within the Flaming Gorge National Recreation Area.

Having initially established its course in Tertiary sediments (from the Green River Lakes, regional volcanism and mountain erosion) the Green River cut through the eastern end of the Uinta Range as it rose from below during the Miocene-Pliocene Uplift.  Today, the northern two-thirds of the Gorge is carved in Eocene deposits while the southern third is lined by a progression of Mesozoic, Paleozoic and Precambrian rock (north to south); along its 91 mile course in the Gorge, the Green River (dammed since 1964) has cut through strata representing at least 700 million years of Earth's history.

As we found out today, the Utah portion of the Flaming Gorge NRA is especially scenic, with steep cliffs that rise 1700 feet above the lake; mountainous terrain surrounds the gorge and road signs introduce visitors to the varied rock strata.  To the north, in Wyoming, the lake shimmers amidst a vast sage grassland, broken by Tertiary domes, buttes and mesas that illustrate the erosive power of the Green River and its tributaries over the past 30 million years.

Tuesday, May 12, 2015

Journey to Flaming Gorge

Though my wife and I have traveled extensively throughout the Western U.S., a visit to Flaming Gorge, on the Wyoming-Utah border, has eluded us.  Over the next few days, we plan to remedy that deficiency.

This afternoon, we'll head west on Interstate 70, climbing to the Continental Divide, dipping through the Blue River Valley, winding across Vail Pass and eventually merging with the Colorado River to snake through Glenwood Canyon.

After a night in Glenwood Springs, we'll leave Interstate 70 at Rifle, angling northwest across the Roan Plateau of northwest Colorado and the Uinta Plateau of northeast Utah, both of which are topped by Eocene sediments of the Green River Formation (see Green River Lakes).  From Vernal, Utah, we'll head north to Flaming Gorge, sculpted by the Green River over the past 30 million years and flooded by Flaming Gorge Lake since 1964; more on the Gorge tomorrow.

Monday, May 11, 2015

Caving to Big Oil

Despite the ecological disaster wrought by the Deepwater Horizon explosion in the Gulf of Mexico, five years ago, the effects of which have yet to be fully determined and addressed, the Obama Administration will allow Shell Oil to drill in the pristine waters of the Arctic Ocean off the coast of Alaska.  While the leases were initially granted by the Bush Administration, permission to drill was delayed until "stringent new regulations" were in place.

Though the Obama Administration has spearheaded efforts to reduce our use of fossil fuels, promote solar and wind energy and protect threatened wilderness areas, one wonders why they are caving to Big Oil at a time when there is a worldwide glut of gas and oil and when the tragic consequences of our dependence on fossil fuels (including transportation spills, groundwater and wetland pollution and global warming, among many others) are becoming more and more evident.  To assume that strict drilling regulations will protect the fragile yet treacherous environment of the Arctic Sea is pure folly.

Unfortunately, the political influence of Big Oil trumps any perceived shift toward clean, renewable energy.  In the meantime, as we lurch from one ecological crisis to another, the welfare of our planet, with its magnificent diversity of life, is placed at risk.  The political courage to protect natural ecosystems from the gluttonous adventurism of the Oil & Gas Industry appears to be lacking in our country and across the globe.

Sunday, May 10, 2015

On the Storm's Cold Side

At our Littleton, Colorado, farm, the rain began to change to snow just after 7PM last evening.  A potent upslope flow on the backside (north and west) of the massive spring storm had dropped the air temperature into the mid 30s (F) and, over the next eight hours, five inches of heavy, wet snow accumulated on the grass and trees.

Fully leafed, the smaller trees and shrubs are bent toward the ground by their heavy white cargo while a few branches broke from the larger trees.  This morning, a winter wonderland envelops the farm and the temperature is hovering near 30 F.  Undaunted, the birds are singing as usual, sensing that May will soon re-emerge.

As the storm pushes northeastward, into Nebraska, the upslope flow is breaking down and the morning sun is peeking through the light gray overcast.  Snow showers should end by noon and the potent Colorado sun will bake away the winter glaze; we'll be back in the 70s by Tuesday.  Happy Mother's Day to all who qualify for that beloved title!

Saturday, May 9, 2015

Spring Bird Census

The annual spring bird count was conducted at South Platte Park this morning, a swath of ponds, meadows and riparian woodlands along the South Platte River in Littleton, Colorado.  Setting out from the Interpretive Center by 7AM, the groups endured chilly air and a dense gray overcast, hoping to complete our counts before more heavy rain descended on the valley.

My partner and I were assigned to woodlands and wetlands east of the river.  On our two hour tour, house wrens, tree swallows, American robins, mourning doves and red-winged blackbirds were the most abundant species, followed by mallards, Canada geese, great blue herons, northern flickers, yellow warblers, killdeer, western wood pewees, black-capped chickadees, western kingbirds and white-breasted nuthatches.  Individual sightings included an American kestrel, a spotted sandpiper, a wood duck, a northern oriole and a Say's phoebe.

Though the weather was threatening, the trails were muddy and the sightings were far from exceptional, strolling through that riverine ecosystem was, as always, an enjoyable and rewarding experience.  Besides, until we completed our loop (just before the rain arrived), we remained vigilant for rare migrants and residents, an exercise that, while futile, fueled our enthusiasm.  

Friday, May 8, 2015

Downslope Drying

In the midst of a Front Range deluge, drier air is moving into Metro Denver this evening.  The moisture flow is currently from the south, moving northward along the mountain wall and the adjacent Piedmont.

To our south, heavy rain is falling in Colorado Springs and across the southern flank of the Palmer Divide.  North of that divide (which has an elevation of about 7500 feet), the air descends with the terrain; in concert, its dew point falls (the air is compressed and warms up).  North of Denver, the air rises out of the South Platte Valley and into the foothills; this upsloping air cools, condenses and drops its precipitation once again.

By tomorrow afternoon, the wind is forecast to shift back from the northeast, producing classic upslope conditions along the Front Range, primarily north of the Palmer Divide.  Afternoon thunderstorms will progress to widespread rain which will turn to snow by Sunday morning.  For now, we'll enjoy a brief period of downslope drying.

Thursday, May 7, 2015

Water, Deserts & the Wealthy

In American society, the wealthy enjoy an increasing number of social perks, based on their ability and willingness to pay for them; close-in parking spots, toll lanes and rapid boarding privileges are but a few examples.  It was thus with dismay that I read an article in the NY Times outlining Santa Fe's move to base water price rates on the amount consumed; the report placed a positive spin on that decision, indicating that rates would not significantly rise for lower income citizens while the wealthy will pay heavily to fill their pools and water their lush landscapes.

In my opinion, such a solution to the Western water shortage misses the point and, once again, caters to the lifestyles of the rich and famous.  If one chooses to live in an arid or semiarid environment, one should be willing to forgo green lawns, parks and golf courses and live without private swimming pools.  If the cities must expand their populations to meet economic needs (a questionable premise), new residential complexes should be limited to apartments and condos, not sprawling suburban developments complete with fountains and rolling, irrigated lawns.

We must embrace our natural ecosystems in order to protect them.  If we enjoy a dry, sunny climate, we cannot insist that it look like the Tropics or even the American Midwest.  Fresh water is a finite resource and its excessive diversion from Western ecosystems should not be justified by one's ability to pay for it.

Wednesday, May 6, 2015

The Mystery Legume

When we purchased our Littleton farm, in 1990, I discovered a healthy looking shrub beneath a pair of spruce trees east of the house.  Never much of a botanist, I could not identify the shrub but noticed that its leaves, while softer and paler in color, resembled those of our locust trees.  Small yellow flowers appeared by mid spring and, in mid summer, numerous small spindle-shaped pods hung from its branches, confirming that it is a legume.

Following years of failing to identify the shrub in field guides, the wonders of an internet search finally provided the answer; our lone, hardy shrub is a Siberian Pea Tree.  Native to Siberia, China, Mongolia and Kazakistan, this deciduous shrub has been used for windbreaks across northern regions of the globe; while its seed pods may be cooked for human consumption, the abundant seeds are favored by a wide variety of birds and small mammals, including domestic chickens.

Though our Siberian Pea Tree has adapted well to the Front Range soil and climate (without artificial feeding or watering), it has not spread to other sites on the farm (unlike locusts, lilacs, wild cherries, wild plums and chokecherries); indeed, I have scattered its seed myself without success.  Apparently, this hardy yet attractive shrub is a reluctant parent.

Tuesday, May 5, 2015

Trapped in a Trough

Over the past week, an atmospheric trough has enveloped the Front Range region and much of the Intermountain West.  Reinforced by a series of cold fronts, this dip in the jet stream has spread cool, cloudy, wet weather from the High Plains to the Pacific Northwest.

Low pressure centers, developing along the eastern edge of the trough, have swept Gulf moisture northward through the Heartland, igniting severe thunderstorms across the Plains and producing an upslope flow along the Front Range.  The latter, while studded with strong thunderstorms at times, has primarily brought overcast skies, cool temperatures and pockets of heavy rain.  This pattern, which is expected to persist through the coming weekend, is more reminiscent of the Pacific Northwest than the sunny, semiarid climate of the Front Range.

While this chilly, damp weather may not be ideal for outdoor activity, it is fueling the verdant growth of spring and, for now, eliminating the need for artificial irrigation.  In a dry region that, long ago, outgrew its water supply, any precipitation is more than welcome.


Sunday, May 3, 2015

The Lonesome Towhee

Along the Colorado Front Range, both spotted towhees (permanent residents) and green-tailed towhees (summer residents) prefer the open shrublands of the lower foothills though smaller populations may be found in suburban or rural areas of the urban corridor.  Over the years, some have visited our Littleton farm for periods of time but have always moved on for the breeding season.

Last spring, however, a male spotted towhee appeared on our property and has yet to depart.  Intent on attracting a mate, he sings from dawn to dusk, from late winter to early summer; for the remainder of the year, he is rather quiet, skulking among the shrubs or scratching for insects and seeds beneath the junipers and pinyon pines.  Isolated from his cohorts, his incessant singing has been in vain and I have yet to discover a female spotted towhee on the property.

Social creatures, we humans tend to pity animals that lose contact with their flock or herd.  While I have no ability to relocate our lonesome towhee, he seems content to hang around the farm.  Were he aware that he is but a few miles from the foothills, where his fellow towhees are abundant, he might feel differently!

Saturday, May 2, 2015

Axial Seamount, Iceland & Hawaii

Oceanic volcanic islands develop above mantle hotspots or along mid oceanic ridges where the sea floor is spreading.  The Hawaiian Ridge is an example of the former; its chain of islands, atolls and seamounts formed as the Pacific Plate moved northwestward above a mantle plume, a process that continues today.  Iceland, on the other hand, has formed (and continues to form) above the mid Atlantic ridge, between the North American and Eurasian Plates, where oceanic crust is forming.

Axial Seamount, 300 miles off the coast of northwest Oregon, is the product of both volcanic processes.  Sitting atop the Juan de Fuca Ridge, a spreading center between the Pacific and Juan de Fuca Oceanic Plates (the latter is a remnant of the Farallon Plate), this Seamount is also fed by magma from the Cobb Hotspot; indeed, the Axial Seamount is the youngest (and currently active) formation in a chain that leads northwestward to the Aleutian Trench.  Like the Hawaiian Archipelago, the Cobb-Eickelberg Seamount Chain formed as the Pacific Plate moved northwestward above the hotspot.

Axial Seamount, which appears to have erupted over the past week, rises 3000 feet above the adjacent sections of the Juan de Fuca Ridge; its summit is approximately 1400 meters below the surface of the sea.  Whether it will eventually breach the surface to become a volcanic island will be determined by the ongoing relationship between the Cobb Hotspot and the Juan de Fuca Ridge.

Friday, May 1, 2015

Transition in the Valley

Over the past week, there has been a significant transition in the South Platte Valley.  The last of the winter birds have departed for northern latitudes or for their summer range in the mountains; in concert,  an increasing variety of summer residents have returned to the Valley, having wintered well to our south.

Yesterday, only a few tardy female buffleheads remained on the ponds at South Platte Park, while double-crested cormorants, American white pelicans, western grebes and snowy egrets had settled in for the summer.  In the riparian woodlands, house wrens, yellow warblers, gray catbirds, northern orioles, western pewees and yellow-breasted chats joined the permanent residents.  On our farm, which sits on the west wall of the valley, broad-tailed hummingbirds, house wrens, Say's phoebes, willow flycatchers, mourning doves and chipping sparrows have all made an appearance and Swainson's hawks, back from Argentina, have rejoined our year-round raptors.

Late migrants, such as western tanagers, common nighthawks, lesser goldfinches and violet-green swallows may not appear for another week or so but the great majority of summer residents are now in place.  We'll enjoy their presence until October, when the autumn chill and waning daylight send them south once again.  

Thursday, April 30, 2015

A Handsome Visitor

Over the past few days, a chipping sparrow has visited our Littleton, Colorado, farm.  Easily identified by their slender form, bright rusty crown and light, unstreaked chest and abdomen, these summer residents are rather common along the Front Range urban corridor in mid spring; however most end up nesting in the open ponderosa parklands of the foothills, joining western and mountain bluebirds, pygmy nuthatches, Williamson's sapsuckers, mountain chickadees, Steller's jays, Townsend's solitaires and other montane species.

There they feed primarily on the ground, feasting on both seeds and insects.  Nests, which are placed in shrubs or small trees, consist of dry vegetation and an assortment of man-made and natural materials; chipping sparrows often use animal hair in their nest and were once known as the "hair bird" when horses were our prime mode of transportation and plowing-power.

By late summer, chipping sparrows become less territorial and gather in modest sized flocks.  As cool autumn winds drop across the Rockies, these handsome birds leave for wintering grounds in Florida, Mexico and Southern California.