Nature's Blog

Prairie Streams

2009-11-15T10:34:00.003-06:00

The Great Plains of North America were once covered by a rich prairie ecosystem, which extended from western Ohio to the Rocky Mountain foothills. Today, most of the grasslands have been replaced by cropfields and ranches, significantly diminishing the natural diversity of this region.

Even before the prairies were lost to the farmer's plow and the cattleman's herds, riparian (stream-side) communities were vital to the Great Plains ecology, providing food, shelter, nest sites and natural highways for the varied wildlife of this vast and open country. Now that cropfields cover much of the region, these streams, with their associated woodlands and wetlands, are critical ribbons of natural habitat across an altered landscape; nevertheless, riparian habitats are among our most threatened natural communities, often falling victim to stream diversion and pollution.

Prairie streams concentrate the wild residents of the Great Plains and offer attractive settings for wildlife observation. A wide variety of grassland birds and mammals roost, nest and den along these valleys, which also attract the raptors and carnivores that prey on them. During the spring and fall migrations, these riparian woodlands are ideal for observing songbird migrations and, over the centuries, both wildlife and humans have taken advantage of these bountiful corridors to explore the Heartland and to expand their populations.

Presence of Mind

2009-11-13T06:58:00.003-06:00

Brain power is what separates humans from all other species on our planet. This trait, responsible for all of our accomplishments, from articulate speech to flush toilets, has opened our world to discovery and given us the opportunity to understand the complexities of our environment, our bodies and our relationships. It is, after all, the basis for the human condition.

Despite the many advantages that brain power affords, it also has a tendency to complicate our lives. The capacity for memory, essential to the learning process, opens the door to rumination and regret; in like manner, our ability to anticipate the future often leads to worry and dread. Though the past was not as wonderful as we sometimes remember and the future will not be as daunting as we might imagine, these cerebral preoccupations often cloud and influence our present thoughts and actions.

Indeed, in comparison with many others species, humans have a diminished presence of mind. Not endowed with the acuity of sight, smell and hearing that some animals possess, we depend upon on our higher mental powers to interpret our environment. And, unlike our fellow mammals, we are prone to distraction as the past and future invade our consciousness.

Starling Ballets

2009-11-12T09:03:00.004-06:00

Despised by avid birders and by those who live near their crowded roosts, European starlings have become one of the most successful species in North America, inhabiting almost all of our natural ecosystems. In doing so, they have often displaced native birds by usurping nest cavities or by consuming much of the wild food crop.

Nevertheless, these prolific birds offer some benefits, primarily related to their taste for grubs and other harmful insects. In addition, for those who travel across America's farmlands, they provide entertainment in the form of spectacular aerial displays; these starling ballets are observed during the colder months, when the maligned immigrants gather in huge flocks.

Often first mistaken for a puff of black smoke, the shape of the flock changes constantly as the birds spiral and dip above the countryside, instinctively moving in a coordinated mass. At certain angles, they may disappear from view, suddenly reappearing like a flash card image at a football stadium. To my knowledge, there are no starling choreographers out there but, at times, one wonders.

San Rafael Swell

2009-11-10T09:49:00.004-06:00

Between Green River, Utah, and the eastern edge of the Wasatch Plateau, 70 miles to the west, Interstate 70 crosses a broad ridge, adorned with spectacular rock formations. This topographic dome, up to 40 miles east-west and 100 miles north-south, is known as the San Rafael Swell.

At the onset of the Eocene Period, almost 60 million years ago, this region was characterized by flat terrain, a subsurface layer cake of Paleozoic and Mesozoic sediments overlying the deep, Precambrian basement. At the surface, early Tertiary deposits lay on successively older rock layers (from top to bottom: Cretaceous, Jurassic, Triassic, Permian and older Paleozoic sediments). Then, during the Eocene, the Precambrian basement folded upward as a broad dome, lifting the overlying layers of rock which have since eroded into the formations that we see today; resistant sandstones and limestones form ridges, domes and pinnacles, separated by valleys of softer shale and mudstone.

Atop the Swell, the Tertiary and Mesozoic layers have been stripped away by erosion, leaving a landscape of Permian sandstone; to either side, the traveller passes through successively younger rock formations as he descends from the crest of the dome to the valleys of the San Rafael River (east) and Muddy Creek (west). Prominent hogbacks (reefs) of Dakota Sandstone, Cretaceous in age, rise along the outer edge of the Swell. By crossing the San Rafael Swell on I-70, we pass through almost 200 million years of geologic history....twice.

Tardy Geese

2009-11-09T13:18:00.004-06:00

Most birds migrate in response to the solar cycle, departing their breeding or wintering grounds in concert with a given period of daylight. Waterfowl, on the other hand, tend to move along in response to a combination of weather conditions and food availability; this is especially true during their fall migration when flocks may winter further north if snow and ice are not disrupting their ability to feed.

In Metro Denver, the migrant Canada geese usually arrive during the first week in November, significantly augmenting the smaller populations that are permanent Colorado residents. By now, the fields and skies of the Front Range are usually full of these noisy visitors; in early morning and late afternoon, numerous flocks pass overhead, moving between reservoirs (where they spend the night, safe from predators) and their favorite grasslands. As of today, the influx of migrants has been minimal and I suspect that mild conditions in Canada and the northern U.S. have, as yet, not forced them southward.

Of course, park supervisors and golf course managers hope that they stay to our north, negating an annual cleanup nightmare. But, eventually, the geese will arrive and those of us who enjoy watching their daily travels won't be disappointed.

Plum Creek Valley

2009-11-08T10:42:00.004-06:00

South of Denver, the terrain gradually rises toward the Front Range foothills and the broad Palmer Divide. Drained by Plum Creek and its tributaries, this region has been dissected into a scenic landscape of valleys, ridges and mesas; scrub grasslands cover the lower elevations, juniper and oak thickets adorn the valley walls and stands of ponderosa pine spread across the higher terrain.

Long used for cattle ranching, industry and urban development have spread through the valley over the past century and, in recent decades, suburban sprawl has invaded the uplands. Nevertheless, if one gets away from these sites of human impact, it is easy to appreciate the natural beauty that once characterized all of the Plum Creek Valley. Mule deer are especially common here, feeding along roadways and foraging on the hillsides. Elk winter in the valley and the howls of coyotes echo across this spectacular terrain. Magpies, scrub jays, crows and flickers lend their voice to the wild landscape while golden eagles, prairie falcons, great horned owls and a variety of hawks patrol the region. Though seldom encountered, mountain lions also inhabit the area, attracted by the large deer population.

Such piedmont landscapes, blending the High Plains with the Rocky Mountains, add to the natural diversity of the Front Range environment and offer spectacular settings for wildlife observation. Unfortunately, they also offer appealing sites for residential development and, over time, the natural ecosystem falls victim to human occupation.

Abert's Squirrels

2009-11-06T14:06:00.003-06:00

Those who hike in the ponderosa parklands of our western foothills and mesas have a chance to see Abert's squirrels, one of North America's more unique and interesting mammals. Closely associated with ponderosa pine forests, which are best developed between six and nine thousand feet, these "tassel-eared squirrels" are found in the Rocky Mountain chain, from southern Wyoming to northern Mexico, and across the Colorado Plateau.

Best identified by their prominent ear tufts, Abert's squirrels are primarily arboreal, feeding on the seeds, cones, buds and inner bark of ponderosa pines; they also consume a variety of berries, fungi and carrion. Their nests are constructed with pine needles and twigs and are placed high in mature trees, usually at the junction of a large branch and the central trunk. Mating, which follows a day-long chase by several suitors, occurs in late winter or early spring; 2-4 young are generally born in May or June.

The color of Abert's squirrels varies with the geographic area, ranging from gray to dark brown to black, with white underparts. However, on the Kaibab Plateau, north of the Grand Canyon, a subspecies (known as the Kaibab squirrel) has a black abdomen and a totally white tail; long isolated from populations east of the Colorado River, these Arizona squirrels were once considered to be a separate species. Regardless of their location, the population of Abert's squirrels varies with the health and productivity of the ponderosa pine forest, an ecosystem under continuous assault by the invasion of human communities.

Avian Kites

2009-11-05T19:57:00.004-06:00

All across the Great Plains, hawks, gulls and vultures dipped and soared in the deep blue sky on this sunny, November day. Strong south winds, building ahead of the next cold front, triggered the aerial display and pushed summer-like weather into the region.

As expected, red-tails dominated the show but a few rough-legged hawks were encountered on the High Plains and a golden eagle soared above the Palmer Divide, in eastern Colorado. Even the northern harriers and prairie falcons, which typically fly and hunt close to the ground, could not resist a chance to bank and soar with the others. In central Kansas, just east of Russell, a huge flock of sandhill cranes circled high overhead, seemingly making little progress in the stiff, southerly head winds.

While some (if not most) of these aerialists were in the process of hunting, many seemed to be playing in the steady breeze, dipping and gliding above the wide open terrain. If only we had the ability to join them!

A Mast Bonanza

2009-11-03T08:01:00.004-06:00

Acorns are abundant across central Missouri this year. Well beyond the capacity of natural consumers to eat or store them, the nuts and their fragments coat lawns, roads and walkways.

These nuts are, of course, the fruit of oak trees; more than 600 species of oak can be found across the globe and more than 60 are native to North America. Most oaks are deciduous trees but some, including the live oak of the southeastern U.S., are evergreens; acorn production begins as early as 10 years and as late as 50 years after germination, depending on the species. The white oak family (which also includes bur, gambel, post, chinkapin and chestnut oaks, among others) produce acorns that mature within 1 year and do not have a bitter taste. The red oaks (including scarlet, pin, black, live and willow oaks, among others) produce acorns that mature in 2 years and, due to the presence of tannins, have a bitter taste.

Oaks produce acorns every year but, in mast seasons, which occur every 2-7 years, a dramatic abundance of the nuts are shed; these peak crops result from both innate, natural cycles of the various oak species and seasonal weather variation. This year's mast bonanza will also boost populations of acorn consumers (squirrels, chipmunks, jays, woodpeckers, bears, deer, turkeys, skunks and others) by favoring their winter survival. Native Americans also counted on the mast of autumn and, after leaching tannins from the acorns, would store them for use throughout the colder months.

Big Brother Jupiter

2009-11-02T10:16:00.004-06:00

Jupiter shines high in the southern sky during the evening hours this month. More than five times as far from the sun as we are, this massive gas planet has a diameter that is 11 times the diameter of Earth; indeed, Jupiter's size, relative to the sun, is comparable to Earth's size relative to Jupiter. Though mostly gaseous and without a solid surface, Jupiter's mass is greater than twice that of all the other planets combined.

Composed primarily of hydrogen and helium, Jupiter is thought to have a solid core, similar to that of Earth. Its banded atmosphere, composed of ammonia clouds, is colored by varying quantities of sulfides and hydrocarbons and undergoes constant turbulence due, in part, to the planet's high rotational speed (a full rotation occurs within 10 hours). This rapid rotation also induces a bulging of Jupiter's equatorial region, giving the planet an ovoid shape with flattening at the poles. Four large moons, first observed by Galileo in 1610, are accompanied by almost 60 smaller satellites and several faint rings of dust. The Great Red Spot, Jupiter's most famous and recognizable feature, is a giant storm; possessing the diameter of Earth, it has persisted for at least four centuries.

While astronomers have long credited Jupiter with protecting our inner solar system from wayward comets and asteroids (a trait reinforced by the Shoemaker-Levy 9 impacts in 1994), significant controversy surrounds this theory. There is little doubt that the planet's strong gravitational field alters the course of these roaming chunks of ice and rock but Jupiter's ability to absorb them may not exceed its role in tearing them loose from their benign orbits, to send them hurtling toward the inner planets. Like a big brother, Jupiter may be both our protector and our nemesis!

Nature's Revenge

2009-11-01T15:59:00.003-06:00

After more than six months of being contained, trimmed, beautified and doused with chemicals, nature exerts her revenge on the American suburbanite in November. Showering lawns, gardens, roofs and walkways with a copious mix of leaves, twigs and seed pods, she reminds us that manicured landscapes are not her style.

So the fastidious homeowner, intent on maintaining order, must rake, scoop and remove nature's debris. Ever mindful of his watchful neighbors and the expectations of his community, he recycles this "yard waste" in appropriate bags and places them on the curb (in an orderly fashion) for all to see. He is, indeed, a green-minded citizen.

Those of us more accepting of nature's way are slow to respond to this onslaught of plant debris. We know that wind and rain and snow will remove much of it, that mold and bacteria will degrade the larger components and that a variety of creatures (earthworms, moles, mice, squirrels) will make use of its edible contents. We may clean the gutters and rake some areas but will leave most of nature's debris to nourish and sustain the natural landscape and its residents. Of course, some may blow into the lawn master's yard and end up in those bags.

The Catskills: From Sea to Mountains

2009-10-29T06:41:00.004-06:00

During the Devonian Period, 400-350 million years ago (MYA), the shallow Kaskaskia Sea covered much of eastern North America. When the Avalon subcontinent collided with the northeast edge of North America, about 380 MYA, the Acadian Mountains crumpled skyward, stretching from the mid Atlantic region to the Canadian Maritimes. In concert, downwarping of the crust to the west of this range created a deep bay (the Catskill Basin)in the Kaskaskia Sea; known as the Catskill Sea, this deeper water covered much of New York State and northeastern Pennsylvania.

Throughout the remainder of the Devonian and into the Mississippian Period, the Acadian Mountains eroded from lofty peaks to modest hills; much of the erosional debris was carried into the Catskill Sea, gradually filling its basin and pushing its shoreline further to the west (geologists refer to this process as the Catskill Delta formation). Elsewhere, the Kaskaskia Sea retreated to its component basins, which gradually filled with marine sediments and carboniferous deposits (the latter from vast swamplands and coal forests). Then, from 300-250 MYA, Earth's continents merged into Pangea; the collision of North America and Africa lifted the Southern Appalachians and the adjacent Appalachian Plateau. The latter, comprised of sediments that collected in the Catskill and Allegheny Basins, stretches from New York to Alabama (and was once continuous with the Ozarks of Missouri-Arkansas).

The Catskills of New York and Poconos of Pennsylvania mark the eastern end of the Appalachian Plateau and are composed primarily of debris from the Acadian Mountains, now hardened into sandstones and conglomerate rock. Pleistocene glaciers scoured northern sections of the Plateau and its entire length has been carved into a maze of ridges and valleys by a vast network of streams. Composed of more resistant rock, the Catskills harbor the highest elevations of the Appalachian Plateau; Slide Mountain climbs to nearly 4200 feet and almost 100 peaks rise above 3000 feet.

Song of the Season

2009-10-28T05:50:00.005-06:00

Last evening and this morning, the distinctive song of the white-throated sparrow echoed through our neighborhood. These common sparrows, having bred and summered across the vast North Woods of Canada, winter in eastern and central regions of the U.S., arriving in the latter half of October.

While some move on to the balmy clime of Florida and the Gulf Coast States, our visitors are content to spend their winter in the bleak terrain and harsh conditions of America's Heartland, finding ample sustenance from a wide variety of seeds and berries. After all, they are Canadian natives, oblivious to frigid air and blowing snow. Throughout the colder months, they will be regular visitors to the backyard feeder, scratching for fallen seed during the early morning and late daylight hours.

The homesick song of the white-throated sparrow, translated by birders as "Oh my Canada, Canada, Canada," will fade as winter deepens but will build again during the lengthening days of February; through April, their voice will intensify as these songbirds prepare to depart for their homeland. For now, we welcome their return but know that their tune signals our slide toward winter.

Raw Days

2009-10-26T14:19:00.003-06:00

Characterized by chilly, damp and breezy weather, raw days most often occur in early spring or late autumn. During these periods, winter is battling with the milder seasons and frequent Pacific fronts, guided by an oscillating jet stream, bring unsettled conditions.

The raw days occur on the backside of these fronts, as winds shift from the north and "wrap around" precipitation falls under gray skies. The damp chill on these days, usually accentuated by a brisk, north wind, is generally more uncomfortable than the colder but drier days of mid winter. In addition, raw days occur on the heels of a warm, southerly flow (which develops ahead of the front), producing a dramatic, sudden shift to unpleasant weather.

Today is one of those raw days in Columbia. A chilly, morning drizzle has given way to partial afternoon clearing but a high overcast and northwest winds have prevented any significant warming. As the front continues to move eastward, our winds will shift from the south and sunny skies will prevail until the next Pacific front, just three days away, reminds us that winter is lurking to our north.

The Nature of Teaching

2009-10-25T06:08:00.004-06:00

Having spent most of my career in the private sector, I re-entered academic medicine several years ago and have enjoyed the opportunity to teach once again. After all, teachers are among the most influential people in our lives and it has been an honor to join their ranks.

A teacher does far more than impart factual information. In order to be effective, a good teacher guides students through the process of learning: how to acquire information, how to interpret it and how to apply it to their daily lives. The mechanism by which these goals are achieved is, of course, teacher dependent and some are more successful than others.

But the most vital aspect of teaching is the capacity to instill enthusiasm for a given field of knowledge. Looking back over my own education, I can easily name a handful of teachers who were especially effective in this regard and, it seems to me, it was their personal enthusiasm for the subject that infected me and other students. This quality, the essence of teaching, cannot be learned or fabricated.

Homecoming

2009-10-24T05:57:00.004-06:00

It is Homecoming Weekend in Columbia and, though I am not a graduate of the University of Missouri, it is fun to witness the pride and excitement of those who are or will be. Fortunately, mild, sunny weather is forecast for today's festivities and this evening's game.

Unlike our association with religions, political organizations or homelands, university life is an inclusive experience and, aside from alcohol-fueled scuffles at sporting events, is not a trigger for major conflict. Indeed, for many of us, college is our first significant exposure to individuals from other cultures and countries; as a result, our belief systems (religious, political and otherwise) are challenged, forcing us to actually think through the "truths" that were ingrained in our childhood. Since college is also often our first true experience with personal independence, we are free to absorb and consider these viewpoints without the overriding influence of parents and family (however well intended); of course, one hopes that students arrive at this juncture with guiding principles and a moral compass intact.

Though it is seldom helpful to dwell on our past, with its glory and pain, a chance to gather with old friends and share common memories can be a rewarding experience. After all, many of these people were instrumental in shaping our lives and the political climate that encompassed our college years will bind us for decades to come.

Jim's Lost Season

2009-10-22T05:52:00.003-06:00

Like star athletes whose season was cancelled, Jim Cantore and his fellow hurricane stuntmen have surely had a discouraging summer and fall. While global warming is expected to increase the strength and frequency of tropical storms and the annual shot-in-the-dark forecast from Colorado State predicted a fair amount of activity, the Atlantic hurricane season, with just a few weeks to go, has proved to be a dud.

Stripped of their opportunity to report amidst pounding surf and windblown rain, the Weather Channel crew was forced to settle for inland floods and tornado chasing; Jim visited sites of past glory and, in late summer, had the chance to report from a rowboat, gliding above submerged vehicles.

Almost all of this season's hurricane activity was in the Pacific, with several storms threatening the Baja and a series of massive typhoons creating havoc in Southeast Asia. Predicting the pattern and frequency of tropical cyclones is, obviously, still an inexact science. It will be a long winter for Jim and his team, waiting for the 2010 hurricane season to begin in June. As they say in sports, better luck next year!

Sirius

2009-10-20T12:16:00.003-06:00

This week, in the hour just before dawn, Sirius shines high in the southern sky, just southeast of the Orion constellation. The brightest star in the night sky, Sirius is "only" 8.6 light years from Earth; if it exploded 8 years ago, we won't know until next May.

Actually, Sirius is a binary star system, composed of a large, bright Sirius A star, twice the mass of our sun, and a small, faint Sirius B, only the size of Earth but possessing the mass of our sun. Astronomers believe that the duo formed about 250 million years ago (very recent in the history of the Universe) and that Sirius B, originally a red giant (five times the size of our sun), collapsed into a dense, white dwarf about 120 MYA. The two stars orbit each other every 50 years and are separated by a distance equal to the radius of Uranus' orbit around the sun; of course, from our vantage point, they appear close together.

Also known as the Dog Star, Sirius represented Orion's hunting companion to early human civilizations. Though we now understand its identity and location with more scientific accuracy, it is no less brilliant and no less inspiring.

Maldivians & Polar Bears

2009-10-18T09:34:00.003-06:00

This past week, the governing council of the Maldives, an island chain in the Indian Ocean, planned an undersea meeting to highlight the threat that global warming poses for their island nation. Located about 430 miles southwest of Sri Lanka, the Maldives have a mean elevation below 4 feet, making it the lowest country on Earth. As our planet's climate continues to warm, polar ice will melt and sea level will gradually rise; any low lying, coastal areas will be flooded and, as in the case of the Maldives, become uninhabitable. Furthermore, global warming may have a significant impact on precipitation patterns across the globe, posing a threat to agriculture, ranching and food production.

Like the polar bear of the Arctic, the Maldivian culture may be a victim of global warming, reinforcing the fact that man, like other species, is not immune to natural catastrophe. While current scientific evidence suggests that human activity has played a significant role in the current phase of global warming, Earth's climate has gyrated over its 4.6 billion year history; just within the past 2 million years, continental glaciation has occurred four times and interglacial periods have brought climatic conditions much warmer than those anticipated in the coming decades. Indeed, sea levels have been at least 25 feet higher than they are today.

While we must make every effort to reduce our impact on natural ecosystems, global climate will continue to change, whether induced by supervolcanoes, asteroid strikes, continental drift or fossil fuel consumption. As a consequence, all species, including humans, face potential extinction.

The Prairie Gull

2009-10-17T18:49:00.004-06:00

Nesting in large colonies on prairie wetlands, Franklin's gulls summer across the Great Plains of North America, from central Canada to Montana, the Dakotas and Minnesota. There they feed primarily on insects and continue to do so on their migrations across America's Heartland, often hawking prey above plowed fields and ranchlands.

Those who travel across our vast plains in spring or fall are almost certain to see these gulls, which migrate in sizable flocks and often gather at favored staging areas. Their small size, buoyant flight and preference for grasslands make identification rather easy; Bonaparte's gulls, similar in size and appearance, are common visitors to the Great Lakes region but tend to migrate and winter along the Pacific and Atlantic coasts. By contrast, Franklin's gulls, once called "prairie doves," migrate through the center of our Continent and generally winter south of the United States.

Non-birders and amateur naturalists may be surprised to find these gulls far from any major lakes or rivers. Of course, this reflects the common assumption that "sea gulls" are coastal birds, an image drawn from our trips to the beach. Such assumptions about our natural environment, usually based on limited experience, often prove to be incorrect.

Cranes over Kansas

2009-10-16T20:30:00.004-06:00

Venus and a thumbnail moon beamed from the eastern sky as I left Denver early this morning and began a full day journey to Missouri; the first glow of dawn spread across the horizon, lighting a shelf of clouds far to the east. I caught up with those clouds near Flagler and would soon encounter one of nature's annual spectacles, the autumn migration of sandhill cranes.

The first flock crossed I-70 near Goodland and, over the next 60 miles, I observed many others. Nearing Oakley, I saw an especially large flock moving down from the north and I left the highway to observe the birds more closely and, more importantly, to listen to their distinctive calls as they circled southward on a northwest wind; as with the call of snow geese, the rattling bugle of sandhill cranes never fails to stir my soul.

Having summered and raised their young on tundra, marshy grasslands and open woodlands of Canada, these sandhills were headed for wintering areas in New Mexico, West Texas and Mexico; it was my good fortune to cross their path on this bright October morning. Come spring, they will retrace their route to Canada but will stop to rest and feed along the Platte River in Nebraska, a major staging area for North American cranes and an annual destination for naturalists from across the globe.

Front Range Fox Squirrels

2009-10-15T07:15:00.003-06:00

Eastern fox squirrels are native to southeastern and central regions of North America, from southern Canada to the Gulf Coast. Over the years, these adaptable mammals have spread westward, crossing the Great Plains along wooded river valleys, and reached Colorado via the South Platte and Arkansas River corridors; small populations were also introduced in the State's larger cities.

In their native range, fox squirrels feed primarily on mast (acorns, walnuts, hickory nuts, etc.) but also consume a variety of fruits, seeds, buds and bird eggs. The pioneers that spread west did not find an environment rich in mast and have adjusted their diet accordingly, concentrating on alternative food sources (as above); they have also developed a taste for the cambium layer of tree bark and seem to be especially fond of Russian olive and Siberian elm trees (also introduced species). Needless to say, some of their dietary habits have not been well received by Front Range homeowners.

Faced with a large crop of black walnuts, coating portions of our Missouri yard, I decided to bring a couple bucket loads to our Littleton farm, interested to know how they might be received by our local squirrel population. Before I had time to spread them through our wood border, a few of the fox squirrels had invaded the cache and mounds of black pulp appeared across our property; within 48 hours, all of the walnuts were consumed or buried. It was amazing to find that these Colorado fox squirrels, hundreds of generations removed from the eastern deciduous forest, would so quickly (and efficiently) dispatch this gift from their homeland. Instinctual memory runs deep!

The Paratethys Sea

2009-10-14T09:53:00.004-06:00

During the Triassic Period, some 200 million years ago (MYA), the Tethys Sea opened across Pangea, rifting the northern Continents (Laurasia) from the southern Continents (Gondwana). Over the following Jurassic and Cretaceous Periods, the Atlantic Ocean, Indian Ocean and lesser seaways opened, splitting apart the components of these large land masses and leading to the continental geography that we find today.

During this process, the African Plate drifted northward and rotated counterclockwise, gradually compressing the Tethys Sea and cutting off its eastern connection with the Indian Ocean. In concert, a broad, relatively shallow arm of the Tethys, known as the Paratethys Sea, spread across central Europe and eastern Asia, initially forming a connection between the North Sea and the Mediterranean (the direct remnant of the closing Tethys). Beginning about 40 MYA, compression and subduction along the African-Eurasian margin forced up the Alps and other ranges across the northern edge of the Mediterranean, isolating the Paratethys as a vast inland sea.

Tectonic activity throughout the late Tertiary, followed by periodic glaciation during the Pleistocene, continued to mold the Paratethys Sea as drainage patterns were altered and ocean levels rose and fell. Today, the Aral, Caspian and Black Seas represent remnants of the Paratethys; the first two, entirely cut off from the ocean, have become "saline lakes" while the Black Sea, connected to the Mediterranean via the Bosporus Strait, has settled into a unique, layered hydrology. Cool freshwater, flowing in via the Danube and other Eurasian rivers, overlies warm (but more dense) saltwater that flows up from the Mediterranean; the volume of the latter is balanced by the outflow of freshwater toward the ocean, making the Bosporus Strait a dual flow conduit.

October in the Valley

2009-10-13T15:31:00.005-06:00

A cool but sunny afternoon coaxed me down to the South Platte Valley for a walk along the river and its wetlands. The recent hard freeze has taken a toll on the fall colors but, on the positive side, it eliminated most of the bothersome insects.

Still a bit early in the waterfowl migration season, the number and variety of ducks won't peak for a few more weeks but a fair mix was present on the river, lakes and marsh-lined ponds. Mallards and gadwall were most abundant, joined in the shallows by small flocks of pintail. wigeon and green-winged teal. Aside from a group of ring-necks, the deeper waters were left to the pied-billed grebes; double crested cormorants were noticeably absent, perhaps spooked south by the recent cold weather. Joining these water birds were great blue night herons, black-crowned night herons, belted kingfishers, killdeer and a lone beaver; cruising one of the larger lakes, the beaver looked more playful than industrious on this sunny afternoon.

Down from the mountains, white-crowned sparrows moved along the wood borders, where a variety of regulars (magpies, flickers, chickadees, song sparrows) made their appearance; American kestrels and a red-tailed hawk rounded out the bird observations. All in all, it was an unremarkable, October afternoon in the South Platte Valley.... just what I needed!

A Persistent Upslope

2009-10-12T13:14:00.004-06:00

A shallow but persistent upslope flow has plagued Metro Denver for the past few days. Though the primary storm passed to our north and we were spared the heavy snow, Canadian high pressure, behind the front, has been sweeping cold, relatively humid air into our region; forced to rise across the High Plains, this flow has produced low clouds and fog along the base of the Front Range. Since this cold layer is shallow, a short trip into the mountains leads to clear skies and mild temperatures, offering a convenient escape from our chilly, gray weather.

Today, the wind has shifted from the northeast (the upslope direction for Metro Denver) to the east and the sun is breaking through our clouds and fog. The afternoon temperature should top out near 50 F but enough upslope remains to keep the hazy air in place. By tomorrow, the winds should be more from south and southeast; downsloping across the Palmer Divide, the air will heat up and our persistent fog should rapidly dissipate.

Denver's weather is all about wind direction, which explains both the spring-like outbreaks in winter (brought by downsloping chinooks) and the winter-like conditions in spring (when Pacific storms produce uplsope snow along the Front Range). For now, I anticipate a break in the chilly haze and look forward to a few mild, sunny days before I return to Missouri.