Thursday, May 31, 2007

American Elderberry

American elderberries are blooming in Columbia this week. Elderberries are sprawling, deciduous shrubs that grow to a height of 10 feet or more; they are common in wild areas and are often planted along borders and fencelines. Found in subtropical and temperate zones, more than 30 species grace our planet; 8 of these can be found in North America.

The American elderberry is the common species of the central and eastern U.S. Its small, white flowers, grouped in flat umbrels, bloom in late spring and yield blue-black berries by late summer. These nutritious berries, high in Vitamins A and C, are consumed by a wide variety of wildlife, including songbirds, quail, grouse, wild turkeys, squirrels, raccoons, opossums, field mice and deer. Among the berry-loving songbirds are cardinals, gray catbirds, cedar waxwings, robins, northern orioles, mockingbirds and brown thrashers.

Humans also cherish this fruit, using the berries for pies, jams, syrups and wines. In addition, elderberries have been used for medicinal purposes since the days of Ancient Egypt; the flowers are said to yield a soothing tea, useful in treating the common cold. On the other hand, the leaves and roots of this shrub are toxic to humans and should not be consumed.

Wednesday, May 30, 2007

The Palmer Divide

In the western U.S., weather is all about elevation and wind direction. As winds are forced to rise, the air cools and, depending upon regional temperatures, rain or snow develops. Conversely, as winds descend from higher terrain, the air compresses, warms up and dries out.

The Palmer Divide is a ridge of high ground, extending eastward from the Front Range foothills between Denver and Colorado Springs. Averaging 7000-7500 feet in elevation, it separates the watersheds of the South Platte (to the north) and Arkansas (to the south) Rivers. Though of modest height, this ridge often produces a significant difference in the weather of these two cities; yesterday was no exception.

As a cold front pushed across Colorado, tornadic thunderstorms developed on the eastern Plains. Behind the front, northeast winds pushed cool air toward the Front Range; Denver was in the upper 40s by mid afternoon, with cloudy skies and cold rain. As the air was forced up the foothills and onto the Palmer Divide, a mix of rain and snow developed and more storms were generated. Meanwhile, south of the Divide and only 60 miles from Denver, Colorado Springs basked in partly cloudy skies with a temperature of 72. Had the storm tracked to the south, along the Colorado-New Mexico line, upslope would have come from the southeast and the conditions in Denver and Colorado Springs would have been reversed.

Tuesday, May 29, 2007

Volcanic New Mexico

Mention U.S. volcanoes and most Americans think of Yellowstone, the Pacific Northwest, Alaska and Hawaii. But there is a wealth of volcanic terrain in other parts of the country, especially in the Southwest; New Mexico is rich in Tertiary and Quaternary volcanics.

Perhaps most famous is Shiprock, a volcanic neck that towers 1400 feet above the plains of northwest New Mexico; it is the remnant of a volcano that formed 30 million years ago. The largest volcanic region in the State is the Dantil-Mogollon Field of the southwest quadrant; like the San Juans of Colorado, its ranges were formed from recurrent volcanic eruptions over an extended period of time (in this case, 40-20 million years ago). Sierra Blanca, rising between White Sands National Monument and the city of Roswell, also formed during that period; just northwest of Sierra Blanca is the Carrizozo Lava Flow which developed 5000 years ago and stands out as an elongated, black lake on satellite photos of the State.

Young volcanoes, calderas and lava flows sculpt the landscape of north-central and northeastern New Mexico. Mt. Taylor, a prominant massif northeast of Grants, is a composite volcano of the late Teritary Period, which last erupted 2.5 million years ago. The Taos Plateau, just south of Colorado's San Luis Valley, formed between 5 and 2 million years ago as the Rio Grande Rift began to open; the domes of Mt. San Antonio and Ute Mountain developed during this rifting process and the Rio Grande River has cut a deep gorge through the volcanic plateau, just west of Taos. The Valles Caldera, northwest of Santa Fe, is one of the largest intact calderas on the planet; 10-15 miles wide and up to 2000 feet deep, it is the remnant of a massive volcanic explosion that occured about 1 million years ago.

In northeast New Mexico, the Raton-Clayton volcanic field harbors a mix of cinder cones, lava-topped mesas and shield volcanoes; most prominant is Sierra Grande, a stratovolcano that rises over 2000 feet above the surrounding plains. Northwest of Sierra Grande is Capulin Mountain National Monument, a classic cinder cone which formed 60,000 years ago; a 2-mile toll road takes you to the summit of this young volcano.

Monday, May 28, 2007

War and Speech

Humans are more advanced than "lower animals" in three respects: our brain power, our precision hands and our articulate speech. The latter is a function of the position and structure of our larynx and the refined musculature of our face, tongue and pharynx. While other creatures have superior eyesight, hearing and olfaction, we are the great communicators.

Today, as we honor those who were killed and wounded in our numerous wars, it is clear that man has abused and ignored his communication skills. The power of speech has often been used to foment conflict rather than to quell disagreements. Greed, economic demands, political motivations and religious zealotry have all played a role. Let's hope that, as man evolves, he learns to talk more and fight less; communication is a more effective method of inducing change and it doesn't cause the deaths of young soldiers and innocent civilians.

Sunday, May 27, 2007

Outflow

Yesterday, a southerly breeze swept warm, humid air into Central Missouri, typical conditions for late May. Only the hazy cloudtops to the southwest and a distant rumble of thunder warned of a coming change. Suddenly, about 4 PM, a strong, cold wind swept through Columbia, shaking the trees and dropping the temperature from 80 to 70 in five minutes. The wind died down as quickly as it came, the cluster of storms passed by to our south and, within an hour, the heat and humidity were back.

We had experienced outflow winds from a strong thunderstorm. As they boil up, these storms draw warm, moist air from the surrounding countryside and inject it into the cold, upper layers of the atmosphere. Condensing on the way up, water droplets soon become ice pellets and, depending upon the size and strength of the storm, may progress to large hail. Eventually, this cold air, with its cargo of frozen moisture, plunges toward the ground, producing heavy rain and variable degrees of hail. Striking the ground, this downburst sends out a wave of cold, fast-moving air in all directions.

Yielding a brief respite from the heat and often causing damage to trees and structures, such downdrafts may also give birth to other storms. As this cold, dense air undercuts and lifts the warm, humid air, clouds and showers form above the outflow boundary; some will develop into thunderstorms.

Saturday, May 26, 2007

Sawhill Ponds

Once a blighted swath of gravel pits, the Sawhill Ponds Nature Preserve is now one of the best wetland areas along the Colorado Front Range. Natural and managed restoration has produced an appealing mix of ponds, marsh, meadows and riparian woodlands across the floodplain of Boulder Creek. Owned by the City of Boulder, the refuge is located 4 miles east of the downtown area.

A network of trails takes the visitor through these wetlands, traversing the meadows and running atop earthen levees. Great blue herons, black-crowned night herons, snowy egrets, yellow-headed blackbirds, pied-billed grebes, cinnamon teal, marsh wrens, eastern and western kingbirds, common yellowthroats, western wood pewees, killdeer and spotted sandpipers are among the summer residents. Patient birders may also find American bitterns, soras and Virginia rails hunting in the cattails. Raptors include red-tailed and Swainson's hawks, American kestrels and great horned owls.

In addition to the large variety of birds, visitors may see coyotes, red fox, mule and white-tailed deer, beaver, muskrat and raccoons at Sawhill Ponds. Resident reptiles include painted turtles, garter snakes, king snakes and an occasional rattlesnake; of course, a variety of amphibians also inhabit these wetlands. Plan to visit at dawn or dusk for the best wildlife viewing.

Friday, May 25, 2007

The Bold Flycatcher

The majority of our woodland flycatchers are small, drab and inconspicuous. An exception is the great crested flycatcher which is larger than a cardinal and announces its presence with a loud, piercing "vreeep." Arriving in May, they spend the summer flycatching from treetops and will depart for southern climes by late September.

A pair of great crested flycatchers have settled in our neighborhood this year, roaming among the shade trees in a confident manner. They are easily identified by their large size, yellow abdomen, olive back and rusty wing and tail feathers; their modest crest is not always apparent.
In addition to their bold personality, these flycatchers are known for their nesting habits; using abandoned woodpecker holes or man-made flicker boxes, they mold the nest with a variety of trash and seem especially fond of snake skins.

Thursday, May 24, 2007

Plutons

Plutons are rock formations that form underground as intusions of magma. After cooling beneath the surface, this igneous rock is uplifted by regional tectonic forces and is slowly exposed as the overlying and surrounding sedimentary rocks are eroded away. As one might expect, plutons are found in areas of tectonic and volcanic activity.

Plutons exist in a variety of forms, including stocks, sills and laccoliths; batholiths are massive plutons that usually result from an amalgamation of smaller ones. Stocks are vertical columns of magma that intrude through a series of sedimentary layers; an excellent example is Devil's Tower, in eastern Wyoming, which formed about 60 million years ago as the nearby Black Hills were uplifted. Sills are vertical bands of magma which intrude between sedimentary layers; the most famous sill in North America is the Triassic Palisades Sill along the western side of the Hudson River Valley, which formed as Pangea began to rift apart.

Laccoliths are dome-shaped intrusions of magma which, like sills, develop between layers of sedimentary rock. Well known North American laccoliths include Mt. Katahdin, in Maine, Stone Mountain, near Atlanta, and the laccolithic mountains of eastern and southern Utah; the latter include the La Sal, Henry and Abajo Mountains and the isolated dome of Navaho Mountain; Sleeping Ute Mountain, in southwest Colorado, is also a laccolith. The Katahdin laccolith was intruded during the Acadian Orogeny, 360 million years ago, while Stone Mountain formed as the Blue Ridge was uplifted, 300-250 million years ago. The laccolithic mountains of the Colorado Plateau formed much later, during the regional Miocene Uplift. Finally, the massive Sierra Batholith, composed of three major and numerous smaller plutons, formed from the mid Jurassic through the Cretaceous Periods (see my blog of April 28, 2007).

Wednesday, May 23, 2007

Front Range Shrublands

The life zones of Colorado's Front Range are determined by elevation, which correlates with annual precipitation. The major cities of the Front Range stretch along the Colorado Piedmont, which averages 15 inches of precipitation per year, most of which falls as snow. Receiving just a few inches more, a zone of Shrublands covers the lower slopes of the foothills, ranging in elevation from 6000 to 7500 feet (higher on south-facing hillsides). Adorned with colorful rock formations, this ecosystem harbors a unique mix of vegetation and wildlife.

Yucca-studded grasslands are broken by stands of Gambel's oak, mountain mahogany, wax current, skunkbrush and other drought tolerant shrubs. Willows and cottonwoods line the drainages and pockets of juniper cloak the hillsides; in southern Colorado, pinyon pines are also found in this zone. Scrub jays, black-headed grosbeaks, lesser goldfinches, yellow-breasted chats, white-throated swifts, cliff swallows, Say's phoebes, rufous-sided and green-tailed towhees, rock and canyon wrens, Virginia's warblers, lazuli buntings and common bushtits characterize the bird population; golden eagles are also common here, soaring above the canyons by late morning.

Shrubland mammals include rock squirrels, Colorado chipmunks, raccoons, red fox, coyotes and mule deer; ringtails inhabit this zone in southern Colorado. Mountain lions haunt the shrublands but are primarily nocturnal and rarely seen; a more common danger are western diamondback rattlesnakes, which are best avoided by staying on designated trails. Red Rocks Park, west of Denver, Roxborough State Park, southwest of Denver, and Garden of the Gods, in Colorado Springs, are all excellent places to explore this life zone.

Tuesday, May 22, 2007

Lake Bonneville

The cool, wet climate of the Pleistocene produced a series of large lakes in the Great Basin of the American West. The last of these was Lake Bonneville, which developed 34,000 years ago and eventually spread across most of western Utah and parts of eastern Nevada and southern Idaho. At its peak, 15.5 thousand years ago, this Lake covered 20,000 square miles and had a depth of 1000 feet; its surface elevation was 5100 feet, recorded by the "Bonneville Shoreline," visible across the Great Basin ranges today.

About 14.5 thousand years ago, an alluvial dam along its northern rim (near Red Rock Pass in southern Idaho) broke down, triggering a year-long flood that lowered Lake Bonneville by 350 feet; the resulting "Provo Shoreline" is also evident across the regional mountains. This massive flood scoured the landscape of southern Idaho and greatly augmented flow through the Snake and Columbia Rivers; their impressive canyons are, in part, a product of this deluge. Near the end of the Pleistocene, a gradual warming and drying of the climate caused the smaller lake to receed and disperse into regional basins; today, the Great Salt Lake, Sevier Lake and Utah Lake are all remnants of Lake Bonneville.

Monday, May 21, 2007

Periodic Cicadas

Periodic cicadas, with life cycles of 13 or 17 years, are endemic to eastern North America. In the coming weeks, a brood of 17-year cicadas will emerge across the upper Midwest, from Iowa to Michigan. Their emergence is triggered by soil temperature, which must remain at or above 64 degrees for a week or more; depending on latitude, this generally occurs from mid May to early June.

After emerging from the soil, cicada nymphs climb onto trees, shrubs and other vertical structures and rapidly molt to the adult form, leaving dried skins behind. These adults will live for 3-4 weeks, driving humans crazy with their overwhelming numbers and piercing buzz; the latter is delivered by the male cicada in a fenzied effort to attract a mate. During their brief life span, adult cidadas do not eat and cause no direct injury to foliage; however, the females lay their eggs in the tender parts of trees and shrubs and this can lead to widespread damage to vegetation. Once the eggs hatch, the nymphs drop to the ground and burrow into the soil; there they attach to a root and patiently nourish themselves for the next 17 years.

While making life miserable for suburbanites, adult cicadas provide a wealth of nourishment for birds, raccoons, opossums and squirrels; they are also consumed by cats, dogs and some adventurous humans.

Sunday, May 20, 2007

A New Generation

Though great horned owlets are peering from the nest by March and Canada goslings appear along our lakes in April, it is May that brings us the first wave of newborn wildlife. The chunky young of mourning doves huddle on branches, patiently awaiting morsels from their diligent parents while noisy flocks of newly fledged starlings demand constant attention from their harried providers. Independent from the time they leave the nest, young cottontails forage along the edge of our lawns, ducking into the shrubs at the slightest distrubance.

Out in the swamplands, mother wood ducks usher their young across the wooded ponds where the small, black tadpoles of American toads cloud the shallows. Meanwhile, tiny treefrogs are leaving the water, making a hazardous treck to nearby woodlands; there they will spend the summer feasting on insects and filling the nights with song. In the forest, young woodpeckers peer from their tree cavity for the first time while turkey poults parade behind their mother as she hunts in a clearing.

May is the month when fox and coyote pups first leave the den and early or late day hikers may spot them wrestling in the grass or playfully harassing their parents. Young raccoons, opossums, otters and mink are also gracing the scene this month. Fawns are born in May but are kept hidden in tall vegetation for several weeks; we won't usually encounter them until June.

Saturday, May 19, 2007

The Birds of Summer

Beginning birdwatchers are often surprised by the large number of species that inhabit residential areas of the Midwest. They are most familiar with the common, year-round residents such as robins, cardinals, blue jays, flickers, starlings, crows, mourning doves, chickadees and house sparrows. If they use feeders, they may also be aware of other permanent residents such as house finches, tufted titmice, downy and red-bellied woodpeckers, American goldfinches, Carolina wrens and song sparrows. Those who live in semi-rural areas may see eastern bluebirds, northern mockingbirds and field sparrows and nocturnal birders may turn up an eastern screech owl, barred owl or great horned owl.

Summer birds begin to arrive in mid April and, since most feed on insects and nectar, will depart for southern climes by early October. Gray catbirds, northern orioles, brown thrashers, house wrens, common grackles, yellow warblers, indigo buntings and ruby-throated hummingbirds are among the most common of these summer residents. Less widespread but fairly common are rose-breasted grosbeaks, great crested flycatchers, eastern wood pewees, rufous-sided towhees, chipping sparrows and blue-gray gnatcatchers. Birders who search the skies over residential areas should see chimney swifts, barn and tree swallows, purple finches, common nighthawks, turkey vultures and red-tailed hawks; the latter two species are permanent residents through most of the Midwest. Finally, cedar waxwings, nomads of the bird world, may turn up during any season.

Friday, May 18, 2007

The Nature of Obesity

Obesity, the scourge of American society, is not a natural condition. While some mammals such as hippos, whales, walruses and seals have a thick layer of blubber for buoyancy or insulation, wild animals remain lean for two reasons: they must actively hunt for their food and they eat only when hungry. The same is true for "undeveloped" human populations, for whom physical activity is a matter of survival.

In Western Culture, obesity has become an epidemic. Not merely a lifestyle choice, obesity is a pathologic condition, increasing the risk for hypertension, heart disease, fatty liver disease, adult-onset diabetes, degenerative arthritis and certain cancers. While it does "run in families," this is more related to learned behavior than genetics. Childhood obesity, which develops due to poor dietary habits and inactivity, usually preceeds adult obesity and makes weight loss efforts much more difficult later in life.

Americans are obsessed with diets and "weight control systems" have become a growing segment of our economy. But special diets are unnecessary; obesity more often results from the amount and frequency of food intake and, most importantly, from a lack of exercise. Today, many children are much less active than in previous generations; TV, DVDs and computer games occupy far too much of their time. Only parents can turn the tide of obesity; they must serve as role models, encouraging their children to participate in sports, hiking and other outdoor activities. It is one of the best things your will ever do for them.

Thursday, May 17, 2007

Columbia River Plateau

Covering most of central and eastern Washington, northern and northeastern Oregon and portions of western Idaho, the Columbia River Plateau formed from basalt lava flows, 17 to 6 million years ago; in fact, most of the lava, which spread across 65,000 square miles, poured out within a span of 2 million years (17-15 million years ago). Some 300 major vents have been identified and many more small ones are thought to have existed. One of the basalt flows, which ran from western Idaho to the Pacific, is the longest known lava flow in Earth's history. The thickness of the basalt varies across the Plateau, with some areas exceeding 8000 feet.

The cause for these numerous and massive lava flows is the subject of ongoing scientific debate. Most geologists feel that the rise of the Cascades, which began 36 million years ago and continues today, caused the basin between the Cascades and Rockies to stretch and thin out; the development of mantle plumes beneath the basin may have also played a role. Vents likely occured along fracture lines between the many terrains and island arcs that had merged to form the Pacific Northwest.

Today, the massive Plateau has been molded by the Columbia River and its numerous tributaries; the Snake River, which rises east of the Tetons and flows across southern Idaho, cuts through the southeastern portion of the Plateau before merging with the Columbia. As impressive as the Columbia River Plateau is, its total lava flow is but 10% of the flow at the Deccan Traps (India) and Siberian Traps.

Wednesday, May 16, 2007

Ted Shanks

One of the best birding destinations in the State, the Ted Shanks Conservation Area sits at the confluence of the Salt and Mississippi Rivers in northeast Missouri. A mix of man-made and natural wetlands, this fascinating refuge is accessed by an 11.5 mile tour road; adventurous birders can also walk some of the 35 miles of levees that lace the area. The entrance to the Ted Shanks refuge is via Route TT, off Missouri 79, 14 miles north of Louisiana.

May is an excellent time to visit the preserve; most summer residents have arrived and some spring migrants are still moving north along the Mississippi Valley. Nesting birds of note include least bitterns, king rails, American coot, little blue herons, hooded mergansers, bald eagles, willow flycatchers, Bell's vireos, worm-eating warblers, blue grosbeaks and Le Conte's sparrows. Among the regular spring migrants are horned and eared grebes, American white pelicans, ospreys, white-faced ibis, cattle egrets, Bonaparte's gulls and black terns.

Other common summer residents, such as great blue herons, great egrets, green-backed herons, wood ducks, belted kingfishers, red-shouldered hawks, barred owls, rose-breasted grosbeaks, indigo buntings, eastern phoebes, common yellowthroats and grasshopper sparrows round out the bird population. Resident mammals include beaver, muskrat, river otters, mink and white-tailed deer. Of course, a wide variety of reptiles and amphibians also inhabit the refuge.

Tuesday, May 15, 2007

Canadian High

After a week or more of warm weather, a Canadian front has dropped into the Midwest. Late this morning, it was 78 in Columbia; showers developed in the early afternoon and, by this evening, it was 56 degrees. Tonight's low is expected to be in the upper forties and, as the cool, dry air settles over the Heartland, we will have a few days that feel more like early October than mid May. Winds moving across the north side of the high pressure will bring more chilly weather to New England, with highs expected in the 50s and lows in the 30s.

Such Canadian Highs provide welcome respites from the hot, muggy days of summer and become increasingly common as autumn approaches. This cold front may have the added benefit of triggering showers and thunderstorms across the parched Southeast; the cool temperatures and precipitation should help combat the ongoing wildfires in southern Georgia and northern Florida. Unfortunately, this is forecast to be a "progressive front" which, rather than stalling out, will move rapidly to the east and and take the precipitation out to sea. As the Canadian High heads to the East Coast, backside winds will sweep heat and humidity up from the Gulf of Mexico and more typical, late spring weather will return to the Midwest.

Monday, May 14, 2007

Ruby-throated Hummingbirds

While twenty species of hummingbird can be found in the U.S., the great majority are limited to the southwestern States; only the ruby-throated hummingbird summers in the Midwest and East. Smallest of all birds, hummers are also the only birds capable of flying backward. They use their needle-like bill to feed on nectar from tubular flowers but also feed on small insects and tree sap; the latter is often obtained from sapsucker holes.

Ruby-throated hummingbirds generally arrive in the Midwest by late April and will stay until early October. Common in residential areas, they are easily attracted to red-colored, sugar water feeders; plantings of honeysuckle, trumpet vine, jewelweed, salvia, petunias, bee balm and mimosa will also bring these high-energy birds to your yard. When not feeding or chasing off rivals, hummingbirds rest on wires or thin tree branches.

Both sexes have a metallic green crown, back and wings and a white abdomen; only the male has the bright ruby throat which, at certain angles, may appear black. Females lay two, white, jelly-bean sized eggs in a small, cup-shaped nest; the latter is composed of plant down and spider silk and is usually covered with lichens; two broods may be raised in some years. By early October, the ruby-throats are off to Central or South America, departing before a hard freeze eliminates their food source; amazingly, many of these tiny birds will cross the Gulf of Mexico on their biannual journey.

Sunday, May 13, 2007

Mom's Mitochondria

When we discuss DNA and inheritance, we are generally talking about nuclear DNA, half of which is provided by each parent. But there is also a small amount of mitochondrial DNA in each cell, 37 genes worth, that, in the great majority of species, is inherited purely from the mother. Since this DNA has a predicatable rate of mutation, genetic scientists have been able to use mitochondrial DNA to study the sequence of evolution and species dispersal patterns throughout the history of our planet.

Mitochondria are small organelles within the cytoplasm of our cells that are important in energy production and protein assembly. It is thought that they originated in the early stages of life's history on Earth, when bacteria became incorporated into other single-celled organisms; this likely occured before nucleated cells evolved. In animals that reproduce through sexual mechanisms, only the mitochondria of the egg are preserved; those of the sperm are destroyed during the process of fertilization.

So, on this Mother's Day, when you thank mom for all that she has done, don't forget to mention that mitochondrial DNA. You couldn't live without it!

Saturday, May 12, 2007

The Cottontail Strategy

Cottontails face numerous natural enemies, including coyotes, fox, hawks, owls and snakes. Almost half of their newborns die before six weeks of age, succumbing to cold weather, flooding, lawn mowers and predation by cats, snakes, crows, magpies and weasels. Of course, many cottontails are also killed by human hunters and motorists.

To balance these threats and insure their survival, cottontails are very fertile and produce multiple litters through the course of a year. In Missouri, these common rabbits breed from mid February to early September with many females giving birth to seven or eight litters. Their gestation period is 4 weeks and litters average 4 to 6 bunnies; spring litters tend to be the largest. Some females born in the spring will give birth to their own offspring by late summer.

This survival strategy is also common among small prey animals such as mice, voles and lemmings. When conditions are favorable, such fertility may lead to population explosions and the potential for significant crop loss. It is then that we most appreciate nature's predators.

Friday, May 11, 2007

Humans and Rivers

This week's flooding in Missouri is just the latest saga in man's long, stormy love affair with rivers. Ever since early humans spread across the globe, we have been building camps, towns and cities along these streams, vital channels of water, food and navigation. But more than providing this inate utility, rivers touch something in our souls; despite their power, they evoke a sense of tranquility and we want to live near them.

So we have attempted to control rivers through our use of dams, levees and dredged channels. Confident of our mastery, we have built towns and cities on their floodplains, somehow ignoring how those flat valleys came to be. At the same time, we have destroyed most of the wetlands that once absorbed the seasonal flooding which now ravages our riverside communities.

The Great Midwest Flood of 1993 served notice that we have a limited (and temporary) ability to harness the power of rivers. The sooner we accept this fact, the sooner we'll take a more reasonable approach to floodplain "development." Restoring the wetlands would be a good start!

Thursday, May 10, 2007

Lake Baikal

Lake Baikal, in southeastern Siberia, is surely one of the most fascinating places on Earth. Filling the deepest continental rift on the planet, this lake holds 20% of our liquid fresh water, more than all of America's Great Lakes combined. Baikal is 395 miles long, up to 50 miles in width and averages 1 mile in depth. The rift itself is 5 miles deep but the lake's sediment is 4 miles thick; both the rift and the lake are thought to be 25-30 million years old, making Baikal the deepest, largest (by volume) and oldest freshwater lake on Earth. Surrounded by mountains and filled by more than 300 rivers, Lake Baikal drains to the Arctic Ocean via the Lena River.

More impressive than its size, Lake Baikal is home to over 1000 plant species and more than 1200 animal species, 80% of which are endemic to the lake (they are found nowhere else on the planet). Baikal harbors 56 species of fish, including its famous omul salmon, and is home to the only freshwater seal on Earth, the Baikal seal, locally known as the nerpa. It is thought that these seals migrated from the Arctic Ocean during the late Tertiary Period, when the Lena was a much larger river.

The mountains and taiga surrounding the lake are also rich in wildlife, over 80% of which are endemic to the region. These include brown bears, sable, lynx, moose, reindeer, pikas and the Siberian chipmunk; among the unique bird species are white-tailed eagles and grey herons. The only threat to this natural paradise is, of course, human activity. Regional air pollution is a problem and the pristine lake waters are threatened by effluent from a pulp mill, built on the south shore of Baikal.

Wednesday, May 9, 2007

The Farallon Plate

During the Mesozoic Era, the Age of Dinosaurs, the oceanic Farallon Plate stretched along the west side of the North and South American Plates; at that time, the west coast of North America was at the longitude of central Utah. By the mid Jurassic, about 160 million years ago, the Atlantic Ocean began to open and the American Plates were pushed westward, forcing the Farallon Plate to subduct beneath their western edge.

This subduction of oceanic plate triggered the formation of the Andes in South America and, over time, added a large number of exotic terrains and island arcs to the west coast of North America, building up the Great Basin, California, the Pacific Northwest, British Columbia and Alaska. The Cascades of Washington and Oregon began to form about 36 million years ago as this process continued.

Today, most of the Farallon Plate has disappeared beneath the Americas but three remants persist: the Juan de Fuca Plate along the Pacific Northwest, the Cocos Plate along the west edge of Central America and the Nazca Plate along the west coast of South America. All three are still subducting and volcanism will persist in these areas until either the "Farallon fuel" is used up or the Atlantic stops expanding.

Tuesday, May 8, 2007

Death in the Shallows

Last evening, my wife and I took a walk at the Forum Nature Area, in southwest Columbia. Stretching along the floodplain of Hinkson Creek, this refuge is a pleasing mix of restored prairie, riparian woodlands and seasonal wetlands. On this warm, breezy evening, the frenzied song of cricket frogs echoed through the valley and a pair of barred owls, half a mile apart, called to one another from the creekside forest. Out on the grasslands, a trio of deer browsed in the shadows while bluebirds and tree swallows guarded their nest boxes.

Approaching the west end of the preserve, I noticed a movement in the shallows. We stopped to watch as the tail end of a large black snake writhed about in the water, its head hidden in the marsh grass. I initially thought it had trapped a frog or small mammal against the shoreline but, as its body went limp on the surface, it soon became apparent that the snake was losing this battle. My next thought: a snapping turtle had caught the snake. Sure enough, after a few more spasms from the victim, the monstrous head of a snapper emerged from the lake, the body of the snake protruding from its jaws.

Completing the trail loop, we passed the usually mix of families, couples and dog walkers, all enjoying the pleasant evening. Lost in their conversation and duties, few seemed to notice the abundant wildlife in their midst and none would likely see the remnants of the death struggle. By then, the snapper had towed its prize to the muddy bottom and was chomping away at its carcass. Nature is not always pretty.

Monday, May 7, 2007

Nighthawks

Several hot, humid days have brought the common nighthawks back to Columbia. After a winter in South America, they have been circling northward over the past month and no doubt took advantage of strong southerly winds this weekend to complete their journey.

Most active at dusk, nighthawks are easily identified by their halting flight, white wing patches and distinctive call, a sharp "peent." Flapping and gliding above our cities and suburbs, they feast on flying insects, often gathering near sports fields where the bright lights concentrate their prey. Nighthawks roost and nest on the ground or on flat urban roofs; they are occasionally active during the day, especially after heavy rains send clouds of insects into the air.

Watch for them on calm, summer evenings when they join bats and chimney swifts in the waning daylight. As August gives way to September, nighthawks drift southward in large flocks, never to experience the autumn chill.

Sunday, May 6, 2007

Dome of Drought

For the past two months, a dome of high pressure has been sitting over the southeastern U.S., aggravating a prolonged regional drought. As Pacific fronts move toward this dome, they are deflected to the north and east, depriving the southeast of much needed moisture. Clockwise winds move along the outer edge of the dome, pulling humid Gulf air into the Heartland and bringing heavy rain and severe thunderstorms to the southern Plains and Midwest.

Within the dome, sinking air prevents the development of "pop up" thunderstorms which are usually common in the southeast. Furthermore, the prolonged drought has produced a dry landscape that feeds little moisture to the atmosphere; any showers that do manage to form drop their rain into a low humidity air mass and most of the precipitation evaporates before reaching the ground. Such conditions lead to wildfires, a lowering water table and widespread water shortages. A potent, slow-moving tropical storm may prove to be the only hope for breaking this cycle.

Many of Earth's deserts have developed under similar conditions. They occur at latitudes where high pressure dominates and where the air is sinking. Air warms up and dries out as it sinks and, as noted above, high pressure deflects fronts and prevents cloud formation. Where oceanic currents and jet stream patterns keep such domes in place, deserts form.

Saturday, May 5, 2007

Oil and the Tethys Sea

In the late Triassic, 200 million years ago, Pangea began to rift apart as the Tethys Sea spread east to west, separating the northern and southern Continents. This seaway reached its maximum extent by the middle Jurassic, when it covered a swath that would later become northwest Australia, south-central Asia, southwestern Russia, the Middle East, the Mediterranean basin, the Gulf of Mexico and the Gulf Coast region. Keep in mind that the continents were still pushed together (east to west) at this time; the Atlantic had just begun to open and the Indian Ocean was yet to form.

Today, the Mediterranean Sea, the Black Sea and the Caspian Sea are remnants of the Tethys. Of more significance, oil formed within sediments of this ancient Sea, a degredation product of plankton and other organic marine debris . The oil that is pumped from the Gulf Coast region, the Gulf of Mexico, northern Africa, the Middle East and western Russia lies within Jurassic shale, a sediment of the Tethys. In like manner, the salt domes of the Gulf Coast States, most numerous in Louisiana, were deposited by the Tethys Sea.

It is both fascinating and disturbing to know that this prize of human culture, a source of so much misery and conflict, originated more than 100 million years ago, in the placid waters of the Tethys Sea.

Friday, May 4, 2007

Karst Landscapes

Karst landscapes develop where thick layers of soluble bedrock (limestones or dolomites) lie close to the surface and where plentiful moisture (past or present) has dissolved channels and caverns in this bedrock. Rainfall, snowmelt or groundwater enter cracks in the rock and gradually erode channels; these open tunnels allow more water to flow into the bedrock, leading to the formation of caves and underground streams.

Some of the caves eventually collapse, forming sinkholes and "stealing" flow from surface streams. Where overlying, insoluble rock (such as sandstone) protects the eroded limestone, large, extensive cave systems may develop and "dripstone" formations (stalactites, stalagmites and flowstone) adorn the caverns. All of this underground water eventually returns to the surface via natural springs or enters regional acquifers. Karst topography is thus characterized by rolling terrain with numerous sinkholes and few surface streams. Caves underlie the region and their underground streams may surface some distance away, often emerging from limestone cliffs along a major river.

Tennessee, Kentucky and Missouri harbor a wealth of karst landscape. Tennessee has more caves than any other State and Kentucky is the home of Mammoth Cave; eroded in Mississippian limestone, this is thought to be the most extensive cave system on Earth. Most of Missouri's caves are found across the Ozark Plateau, where Ordovician dolomites predominate; the Mississippian limestones of southwest and central Missouri are also renowned for their karst features.

Thursday, May 3, 2007

The Appalachian Plateau

Stretching from the Catskills of New York to northern Alabama, the Appalachian Plateau is a broad uplift of horizontal, late Paleozoic sediments. The Plateau rose in concert with the southern Appalachian Mountains as North America and Africa collided; this occured during the assembly of Pangea, some 250 million years ago.

Today, the Plateau covers southwestern New York, western Pennsylvania, eastern Ohio, most of West Virginia, eastern Kentucky, central Tennessee and northeastern Alabama. Its component rock layers date from 350 to 250 million years ago (Mississippian, Pennsylvanian and Permian); the Pennsylvanian strata dominate across most of this province and harbor thick seams of coal. Numerous streams, dendritic in pattern, have carved the Plateau into a maze of ridges and valleys. Wild turkey, ruffed grouse, beaver and white-tailed deer typify the resident wildlife; black bear inhabit some portions of the Plateau.

In New York and northern Ohio, glaciation has obscured its northern and western margin but, from central Ohio southward, the western edge of the Plateau rises 500 feet or more above the Central Lowlands of the Midwest. In some areas, especially near Berea, Kentucky, a chain of knobs runs along the western edge, erosional remnants from the Plateau's original western boundary. Often called the Cumberland Plateau in southern Kentucky and Tennessee, the Appalachian Plateau gives may to the Ridge and Valley Province of the Appalachian Mountains on its east side. This boundary is especially conspicuous in Pennsylvania, where the "Allegheny Front" of the Plateau looms as a high wall to the west of the mountain ridges.

Wednesday, May 2, 2007

Colorado's Birding Capitol

Barr Lake State Park, northeast of Denver, is the undisputed capitol of birding in Colorado. Home to the Colorado Bird Observatory, this Park has recorded more bird species than any other location in the State. Early May is one of the best times to visit; most summer residents have arrived and migrants are still moving across the Plains, heading for the mountains or more northern breeding areas.

Centered on a large irrigation reservoir, this State Park is a mosaic of grasslands, marsh, riparian woods and open lake waters; an earthen trail encircles the reservoir and several boardwalks take visitors across the adjacent wetlands. Bald eagles, cormorants, western grebes and several herons nest here and American white pelicans summer on the lake. Regular migrants and visitors include snowy egrets, white-faced ibis, ospreys, Wilson's phalaropes and a wide variety of waterfowl, gulls, terns and shorebirds.

Woodlands along the southern and eastern shores of the reservoir fill with songbirds by early May. Northern orioles, house wrens, common yellowthroats and yellow warblers are especially common; migrants include Swainson's thrushes, Wilson's warblers, white-crowned sparrows and yellow-rumped warblers. Eastern and western kingbirds, black-billed magpies, Swainson's hawks, ring-necked pheasants, blue grosbeaks, western meadowlarks and loggerhead shrikes inhabit the Park's grasslands, where red fox and coyotes are often seen at dawn or dusk.

Tuesday, May 1, 2007

Cane Creek

Cane Creek State Park, in northern Ohio, sits on the south shore of Lake Erie, between Toledo and Sandusky. This relatively small Park, which lies along the east border of the Ottawa National Wildlife Refuge, harbors a tract of forest which fills with migrant songbirds in early May; it is especially well known for its large number and variety of migrant warblers.

Streaming north toward their Canadian breeding grounds, these birds suddenly encounter the broad expanse of Lake Erie and stop to rest and feed in the Cane Creek woods. A boardwalk leads birders and photographers through this lakeside woodland, yielding close encounters with an amazing variety of migrants. So, if you don't mind birding in a crowd and are still missing a few warblers from your life list, you should consider a visit to Cane Creek!

Cane Creek State Park is accessed off State Route 2, near Oak Harbor, Ohio. The Park lies at the northwest corner of the Magee Marsh Wildlife Area.