Unsettled Basement

Residents of east-central Oklahoma were shaken by two small earthquakes yesterday. While we usually associate earthquakes with the Pacific Rim, they are not uncommon across the "stable" continental platforms, generally occuring in the area of old sutures or past rifts.

Yesterday's tremors originated along the Humboldt Fault, which runs along the east edge of the Nehama Ridge. The latter is a crumpled uplift of the deep, Precambrian granite, which runs from Omaha, Nebraska, to Oklahoma City. The Ridge, itself, resulted from the formation of the Mid-Continent Rift, an opening in the North American plate that occured 1.1 billion years ago. This healed rift lies about 50 miles west of the Nehama Ridge; as it opened, the rift filled with volcanic magma and deformed the basement rocks to either side. Had the rifting process continued, proto-North America would have split into two continents.

Earthquakes are fairly common along the Nehama Ridge but most are "microquakes," too weak to be felt. The strongest recorded Nehama quake occured in 1867, in eastern Kansas; that magnitude 5.2 earthquake damaged buildings. Yesterdays tremors only rattled nerves.

The Darkest Day

The winter solstice is starting out extra dark and gloomy today. Warm air has moved in over the cold, damp ground, producing dense fog throughout the area. We should see the sun by late morning but, on this shortest day of the year, it will set by late afternoon.

While the days will lengthen from now until June 21, the coldest weeks are still ahead. The sun angle will be too low to provide much direct heating until mid February or so and we'll have to depend on southerly winds to bring relief from the winter chill. But the march toward spring begins today and we should notice the longer days and shorter shadows within a month.

Upslope

Heavy snow and blizzard conditions are forecast for Metro Denver and other Front Range cities today. Contrary to public perception, this is not a common event during the winter months. Since winter storms usually arrive from the north or west, the storm dynamics produce only moderate snowfall in Denver. Western storms lose most of their precipitation as they cross the mountains and northern fronts are generally attached to low pressure areas that are north of the Front Range region. In the latter case, Denver receives "backside" snow as the primary storm moves eastward.

Today's event is more typical of spring, "upslope" storms. The center of circulation has moved across the southwest and is now in northeast New Mexico. Winds flow counter-clockwise around this area of low pressure, pulling in Gulf-humidified air from the Plains. As this moisture-laden air moves westward, it is forced to rise by the higher terrain and, eventually, by the Front Range of the Rockies. Rising air cools and, depending on regional temperatures, loses its moisture as rain or snow. Twenty inches of snow are expected in Denver.

Nature Rules

The apparent death of three climbers on Mt. Hood this week reminds us all that man, with his technology, skills and brain power, is no match for the forces of nature. Katrina demonstrated the folly of living below sea level in hurricane zones and the floods of 1993 convinced many to finally abandon the Mississippi floodplain.

While we should not dwell on life's dangers and should never give up our thirst for adventure, we must also realize that we will never tame nature. It makes more sense to respect her power and to learn how to safely function within her domain. In the end, nature rules.

Ordovicia

Winter is a good time to study the geology and landscape of our home planet. Barren trees and flattened grasslands yield broader vistas and we are not distracted by the abundance of plant and animal life that characterize our warmer months. Those interested in hunting for fossils of early marine life should consider a visit to my home town of Cincinnati, Ohio.

The Ordovician shales and limestones of Greater Cincinnati were deposited in shallow seas, some 500 million years ago (60 million years before plants first colonized the land). An upward bowing of the deeper Precambrian rocks, known as "the Cincinnati Arch," has kept these ancient marine sediments near the surface, where they are now exposed by roadcuts and stream erosion. Famous for their cargo of bryozoan, brachiopod and trilobite fossils, these rocks extend into southeastern Indiana and down through the Bluegrass region of northern Kentucky.

Man and Evil

My wife and I saw Apocalypto this afternoon. It was an interesting movie with an historical plot and mystical themes. And, for me, it reinforced the fact that man is the only species on this planet that has the capacity for evil behavior.

While other animals kill or inflict injury in response to a survival instinct, man often kills or maims out of ignorance, irrational fear, zealotry or greed. Worse yet, he teaches his young to do the same.

Counting Crows

The annual Audubon Christmas Bird Count took place today. Sponsored by the National Audubon Society, the project is designed to monitor the population of wintering birds in an effort to identify the impact that disease or environmental factors may be having on various avian species. Our group of four was assigned an area between Columbia and Ashland, stretching eastward from the Missouri River. This region is characterized by rolling farmlands, forested hills and riparian woodlands. It was a very mild day, with cloudy skies and a high in the low sixties; however, a steady south wind blew throughout the day and, as most birders know, wind keeps birds in protected areas (and out of sight).

Nevertheless, we saw a fair number of species, with crows, starlings, red-winged blackbirds and, somewhat surprisingly, eastern bluebirds topping the list. The usual mix of common birds, such as red-tailed hawks, cardinals, flickers, red-bellied woodpeckers, chickadees and blue jays, were found in expected numbers. However, ground feeders, including sparrows, juncos and mourning doves, were significantly reduced and we wondered if the recent heavy snow had forced many to leave the area. Highlights of the day included bald eagles, a barred owl and a red-shouldered hawk.

The Glaciated Plain

Driving north from Columbia, one soon enters the vast Glaciated Plain of the American Midwest. This province, which stretches from central Ohio to the eastern Dakotas, was flattened by the Pleistocene Ice Sheets and enriched by their till. Once the last glacier retreated into Canada, some 12,000 years ago, a rich, tallgrass prairie spread across the region. Periodic wildfires, intermittent drought and the grazing of huge bison herds kept the forest at bay and trees were restricted to the stream beds and river valleys.

The arrival of white settlers dramatically changed the ecosystem of this province. The prairie was plowed, the bison were killed and wildfires were suppressed. Today, the Glaciated Plain has become the great Corn Belt of North America.

Northwest Hurricane

While we usually associate hurricanes with tropical islands and the Southeast coast, a monster storm is brewing in the Pacific Northwest. Triggered by the confluence of jet streams, the storm is expected to hit Washington and Oregon tonight, pummeling the coast with 20-30 foot waves and hurricane-force winds. The northern branch of the jet stream will bring Arctic air from the Gulf of Alaska while the southern branch will send a stream of warm, moist air from the central Pacific; the collision of these air masses, in combination with the merging jet streams, will generate the storm. Torrential rain is expected in the lowlands while heavy snows and high winds will produce blizzard conditions throughout the Cascades.

Meanwhile, the rest of the country is enjoying mild weather with temperatures well above average. We should hit 60 degrees in Columbia today, with partly cloudy skies and a gentle south breeze.

Ribbon of Life

On my frequent trips to our Colorado farm, I always plan a walk along the South Platte River. Coursing through a greenbelt of meadows, wetlands, ponds and cottonwood groves, the river attracts a wide variety of wildlife throughout the year. This is especially true during the winter months when ponds and lakes freeze over.

Joining the year-round waterfowl are wintering species such as green-winged teal, common mergansers, buffleheads, ring-necked ducks and common goldeneyes. Some great blue herons stay for the winter and even an occasional black-crowned night heron declines to head south. Belted kingfishers noisily patrol the river while hawks, kestrels and great horned owls hunt for mice and cottontails on the streamside meadows. Bald eagles are common winter visitors along the South Platte, feeding on fish and waterfowl. Resident mammals include muskrat, beaver, red fox, deer and coyotes.

The Source

Almost all of the rain and snow that falls on the American Heartland originates in the Gulf of Mexico. While the precipitation is triggered by fronts from the north or west, these storms bring little moisture with them. Arctic fronts are accompanied by cold, dry air and Pacific storms lose most of their moisture as they cross the Sierra Nevada and Rocky Mountains.

However, ahead of these fronts, warm, moist air moves up from the Gulf of Mexico. If low pressure zones along the fronts are potent enough to lift this moisture-laden air, precipitation occurs. So, as you gaze upon that snow in your yard, realize that it may have been lapping the shores of Cozumel last week!

The Prolific Immigrant

Backlit by a street lamp, an opossum shuffled across our road in the early morning darkness. It was no doubt hungry after riding out the big snowstorm in some abandoned burrow or tree cavity. While common in our region, this nocturnal wanderer has naked ears and tail, making it prone to frostbite.

Our country's only marsupial is a native of South America but can now be found as far north as southern Canada. Despite its tiny brain and poor eyesight, the opossum has achieved this expansion for two reasons: it is a prolific breeder and will eat almost anything. Though solitary by nature, opossums breed twice a year and females produce litters of 8-13 kits. Adults usually forage at night for insects, berries, eggs, worms, mice and carrion; they are, themselves, prey for fox, coyotes and owls (not to mention their major contribution to roadkill).

December Thaw

The ice, snow and frigid temperatures of the past week are giving way to mild conditions as the jet stream returns to the Canadian border. Flowing west to east, this steering current will direct Pacific fronts across the lower forty-eight while keeping the arctic air to our north. Several of these fronts are expected over the next week, triggering snow in the western mountains and rain showers at the lower elevations of the Midwest and Southeast. With highs in the fifties and lows near freezing, most of our snowpack should disappear in the coming days.

This erratic weather is typical of the American Midwest and makes life more interesting. While I enjoy vacations to the Tropics and long to visit Alaska, I prefer living in the Temperate Zone where plants and animals (humans included) must adapt to an ever-changing climate.

We are History

Mention natural history and most people think of primordial seas, dinosaurs and Neandertals. But evolution of the Earth and its inhabitants continues today. Continents move and rift, oceans open and close, the climate remains in flux and species evolve and disappear. One has only to look at the record of earthquakes, tsunamis and volcanic eruptions over the past few decades to understand that this is true.

Current scientific evidence suggests that the Big Bang occured some 13.7 billion years ago. Our own species appeared only 125,000 years ago and the human life span is in the order of 78 years. It is no wonder that our perspective leads us to false assumptions. Humans are part of natural history and, assuming we don't destroy our environment first, our species will evolve into others in the distant future.

The Flying Tiger

The cold, dark months are upon us, the season of the flying tiger. More properly called the great horned owl, this nocturnal predator is easily identified by its large size, bulky shape, yellow eyes and prominant ear tufts. Like its feline namesake, this raptor is both a loner and a ferocious hunter.

Great horned owls are fairly common throughout most of the country. They usually roost in dense woods, emerging at dusk to hunt on fields and grasslands. While they do feed on mice and voles, these owls prefer larger prey such as cottontails, skunk and grouse; they have even been known to kill ground hogs and wild turkey. Their deep hoots become more common as fall gives way to winter, heralding the onset of their breeding season. Often using the abandoned nests of hawks and magpies, great horned owls lay their eggs by late February and their downy young are peering from the nest before spring.

Polar Express

The jet stream has dipped once again, this time over the eastern half of the country. As a result, arctic air is plunging into the upper Midwest, producing lake-effect snows on the lee side of the Great Lakes. While the core of this frigid air will remain near the Lakes, the front will drop far to the south, bringing a hard freeze to the northern Gulf Coast. In fact, this will be the coldest air to reach the Southeast in three years.

On the positive side, a high-pressure ridge will quickly build in from the west, the polar air will be shoved off to the northeast and daytime temperatures should soon return to normal. Also, since the air is dry and no potent storms are developing along the front, heavy snow will be limited to the Great Lakes region. In mid Missouri, we'll have sunny skies with a high near 20.

Refuge

My wife and I bought a small farm in Littleton, Colorado, in 1990. Overlooking the valley of the South Platte River, the area was a mosaic of fields, ranchlands and housing developments. On our evening walks, we were occasionally treated to the sight of a fox, hunting along the edge of a pasture.

Since that time, most of the fields and farmlands have become suburban neighborhoods and, ironically, our fox sightings are now a daily event. One of the last remaining open spaces in the area, our 3-acre plot has become a refuge for displaced wildlife and a pair of red fox live beneath our barn. Each spring they produce a litter of pups, which roam our property like pet dogs; even the parents lounge on the grass or curl up on the mulch pile, oblivious to our presence. Remnants of their prey litter the fields and their eerie cries jar us awake on cold winter nights.

In a way, our farm is a microcosm of what is happening across the globe. Suburban sprawl, industrial pollution, the drainage of wetlands and the clearance of forest are eliminating natural habitat, displacing wildlife and changing our planet's ecology. If we are to protect the species that remain, including our own, we must stop the destruction of wilderness.

Backyard Killer

The neighborhood crows were having a fit this afternoon and, by the intensity and persistence of their calls, I knew they had cornered a hawk or owl. Sure enough, a sharp-shinned hawk was perched on a limb of our large walnut tree, a songbird in its talons. The crow patrol had settled in surrounding trees, scolding the enemy from all directions.

Sharp-shins are members of the accipiter family. Equipped with short, powerful wings and a long tail, they cruise through open woodlands, hunting for songbirds. They are fairly common in Missouri throughout the colder months and often turn up in residential areas, where backyard feeders concentrate their prey.

Moon Shadows

A brilliant full moon lit the eastern sky last evening and cast deep shadows on our snowy landscape. Such a scene would have been even more spectacular millions of years ago, when the moon was much closer to Earth. Since it formed, the moon has been drifting away from its mother ship, currently at a rate of 4 cm per year!

Modern scientific evidence suggests that the moon formed after the Earth collided with a small planet, some 4.5 billion years ago. This collision ejected a mass of molten debris which coalesced into our lone satellite; the eliptical orbit of the moon, which has an average radius of 240,000 miles, is deflected from the orbital plane of our solar system, lending support to this theory.

Life in the Snow

Unlike humans, wildlife is little affected by the heavy snowfall. Squirrels find plenty to eat in the treetops and tree-feeding birds, such as chickadees, titmice, woodpeckers and nuthatches are not impacted at all. Some mammals, including fox, raccoons, opossums, skunks and cottontails, usually den up until conditions improve while voles and mice remain active beneath the snow, less vulnerable to the hawks and owls that prey on them. River otters, which feed on fish, mollusks and crustaceans, no doubt enjoy the chance to slide and frolic in the snow.

Berry-loving bluebirds, robins, waxwings, cardinals and mockingbirds should have no problems, but ground feeders, such as sparrows, juncos and mourning doves will have to improvise for now, looking for open areas around buildings and scratching for seeds beneath dense thickets or evergreen shrubs. Young and aging deer are also vulnerable to these storms and are more easily killed by coyotes. Those that do succumb to the weather or predation will provide winter sustenance for fox, vultures, crows and field mice.

A Heat Shield of Snow

This week's storm left a wide swath of deep snow from northern Texas to southern Wisconsin. Until the snow melts, cities and towns within this belt will have lower temperatures than nearby snow-free areas. Yesterday, Wichita, Kansas, which received ten inches of snow, had a high temperature of 32 degrees while Hutchinson, a short distance to the northwest (but out of the snow belt), reached a high of 47.

Some of this cooling effect is due to the massive amount of snow itself, which refrigerates the surrounding air. In addition, the heavy snow blanket both insulates the air from the warmth of the underlying earth and reflects solar radiation, thereby reducing heat from the sun. Here in Columbia, we had a beautiful, sunny day to dig out our cars but the temperature struggled to reach the freezing mark.

Snowstorm

Up to 20 inches of sleet and snow fell across central Missouri during the night, bringing human travel to a hault. I-70 was closed from Marshall to Kingdom City and both U.S. 63 and U.S. 54 were shut down. The intense storm, which dropped 1-2 inches per hour at times, included snow thunderstorms, a sign of high altitude development.

But the day turned sunny and bright and a gentle south wind indicated that the storm had moved quickly to the northeast. Life will soon return to normal and we'll go back to thinking that man rules this planet.