A Tardy Southwest Monsoon

Monsoon thunderstorms generally begin to develop across the Desert Southwest by mid July, spreading northward over the following month.  In desert areas, the storms bring welcome rain but often cause flash flooding and haboobs (dust storms).

This year, persistent high pressure over the Desert Southwest has produced relentless sunshine and oppressive heat; it has also shut off the monsoon flow.  By mid summer, high pressure over the Southern Plains usually combines with low pressure over the Baja region to sweep in moisture from the Gulf of Mexico and the Sea of Cortez, igniting the storms.  There is some evidence this week that the high pressure dome over the Southwest is finally shifting eastward, allowing the humid monsoon winds to enter the Sonoran and Chihuahuan Deserts.

While the Southwest Monsoon generally reaches the Colorado Front Range during the second half of August, we have been receiving regular, late-day thunderstorms throughout July.  These storms, in part, have resulted from the persistent high pressure over the Desert Southwest, which has shunted Pacific moisture to the north of the Four Corners region.  Stagnant weather patterns often benefit one geographic area at the expense of another.

Grasshoppers Invade Las Vegas

Reminiscent of a story from Scripture, hordes of grasshoppers have invaded Sin City this week.  But unlike assumptions offered in the Bible, we have a modern scientific explanation for this scourge.

As explained by an entomologist on the Weather Channel this evening, the wet winter and early spring across the Desert Southwest produced an abundance of food for this year's grasshopper population, resulting in large swarms that may cause some agricultural damage in the region.  Furthermore, the species that has invaded Las Vegas, Nevada, is attracted to light and there are few places on this planet more thoroughly illuminated than the Vegas Strip.

So, it appears that the residents of and visitors to this Entertainment Mecca are being inconvenienced more for the city's light pollution than for certain behaviors that are encouraged there.  I'm sure some evangelical ministers may disagree.

Falling Population Growth

Earlier this week, I watched a news program that revealed the U.S. population growth rate is falling.  This is a consequence of women putting off pregnancy until later in life and a slight contraction of life expectancy.  The reporters were a bit alarmed by the data, focusing on the economic impact of fewer consumers.

But, for anyone concerned about global warming and the health of natural ecosystems, this is good news, though the benefits will likely be outweighed by continued high fertility rates in developing countries.  Human overpopulation, recognized as an environmental threat for at least 50 years, places stress on marine and terrestrial ecosystems across the globe; depletion of natural resources, pollution, climate change and habitat destruction all play a role.

No doubt, corporations and investors are alarmed by the prospect of diminished global consumption.  But, unless we reign in our burgeoning population, there will be far greater impacts on the economy (and on the welfare of human civilization) as the health of Planet Earth continues to deteriorate.

Steady State

For the naturalist, mid summer is the closest nature comes to a steady state.  The weather varies little from day to day, plants are maturing but the explosive growth of spring has ended and the new generations of birds and mammals are increasingly independent.

Migrant flocks of shorebirds are now drifting into our wetlands but the massive exodus of songbirds, waterfowl and some raptors is still months away.  Oppressive heat suppresses daytime activity for most birds and mammals and has taken a toll on the verdant landscape of spring and early summer.  Even the atmospheric turmoil of that period has settled into a predictable pattern of daytime heat and evening thunderstorms.

Most of us limit our outdoor activity to the morning or late daylight hours and our expectation for new discoveries is at an annual low.  Only the amphibians, reptiles and insects thrive in the cauldron of mid summer and many humans, myself included, yearn for the cool change of autumn and the natural invigoration that comes with that season.

Hackberry Trees

Other than New Mexico locust trees and chokecherry shrubs, which reproduce by both seed and suckering, hackberries are among the most common trees on our Littleton farm.  Their small berries are eaten by songbirds and small mammals alike, providing a reliable means of seed dispersal.

Represented by numerous species across the Northern Hemisphere, hackberry trees tolerate a wide range of soil conditions though they are most common on floodplains and have long been used to stabilize river banks.  Species found in Western North America are drought tolerant, explaining their ease of propagation on our property.  Their relatively soft wood has proven to be of little value for construction purposes and these trees, which usually grow in mixed woodlands, have been primarily harvested for firewood.

Though not especially attractive (their rough leaves often harbor insect galls) and generally of modest height in the West, hackberries offer maintenance-free greenery and food for a large variety of wildlife.  What better colonizer to host in this semi-arid environment?

Relief from the North

Yesterday, we returned to our Littleton farm to find that several days of extreme heat and bright sunshine had taken a toll on the vegetation.  The leaves of our native shrubs were drooping and our "lawns" and pastures were more brown than green.

Fortunately, a cold front dipped through northeastern Colorado last night, protecting us (for now) from the hot domes of high pressure that sit over the Eastern U.S. and the Desert Southwest.  Our afternoon high was almost 20 degrees (F) cooler than it was yesterday and clockwise winds around the center of high pressure (now over the western Dakotas) ignited afternoon thunderstorms, bringing welcome rain and dropping the temperature into the sixties.

This welcome relief from our recent heat wave should last a couple of days before the atmospheric ridge from the Desert Southwest expands northward once again.  It's a battle of high pressure domes and most of us along the Front Range are surely rooting for our protector from the Northern Plains.

Through the Black Hills and Beyond

After a night in Spearfish, South Dakota, we started back toward Denver this morning and decided to cut through the Black Hills en route.  Fortunately, we chose to start that journey along Route 14A, which climbs through the scenic canyon of Spearfish Creek, lined with sheer cliffs of Mississippian limestone; several beautiful waterfalls adorn the canyon, one of which, Roughlock Falls, is a complex series of cascades at the head of Little Spearfish Canyon, perhaps the most beautiful location in the Black Hills.

After passing through Lead, we continued southward on U.S. 385, passing through some of the least developed regions of the National Forest and purposely avoiding some the popular tourist sites (which we have visited in the past).  Finally dropping from the Black Hills uplift, south of Wind Cave National Park, we crossed the rolling terrain of the Missouri Plateau, drained by the Cheyenne and White Rivers.

Just south of Chadron, Nebraska, we climbed through the Pine Ridge Escarpment and continued southward across the High Plains, highlighted by a westward extension of the Nebraska Sandhills, south of Alliance.  After crossing the broad North Platte Valley, we stopped for the night in Sidney, Nebraska; we'll return to our Littleton farm tomorrow and finally confront the ongoing heat wave in Colorado.

Journey to Devils Tower

Leaving Laramie, Wyoming, this morning, we headed east on Interstate 80, climbing into the Laramie Mountains.  Beyond the pass, we began a long descent on The Gangplank and then switched to I-25 North at Cheyenne.  This highway parallels the Laramie Range, initially at a distance and then at close range near Wheatland, where Laramie Peak (10,500 feet) looms to the northwest and where the Interstate crosses the Laramie River.

Farther north, after passing the Glendo Reservoir and crossing the North Platte River, we headed east on US 18 to Lusk, crossing nondescript grasslands along the way.  At Lusk, we turned north on US 85, soon driving through a scenic landscape of hills and mesas and crossing the upper Cheyenne River.  Nearing Newcastle, yellow sweet clover blanketed the hills and valleys and bee-hive boxes were spaced along the highway; north of Newcastle, US 85 undulates through the west edge of the Black Hills, where Paleozoic redbeds adorn the scenery.  At Four Corners, we cut northwest on Route 585 to Sundance and then followed Routes 14 and 24 north to Devils Tower, America's first National Monument (established by Theodore Roosevelt in 1906).

The geology and natural history of Devils Tower is described in an earlier post (see link) and I will not repeat myself in this one.  On this mild day in mid July, we were greeted by throngs of fellow tourists and by an approaching summer thunderstorm.  Though we did enter the Monument and joined a parade of humans on the Tower Trail that circles the famous landmark, Devils Tower is best appreciated at a distance, where one can observe its placement in the landscape and view its grandeur in relative solitude.

Curt Gowdy State Park

Curt Gowdy State Park, named for the sportscaster and native of Wyoming, stretches across the eastern flank of the Laramie Mountains, west of Cheyenne.  The Laramies are a broad uplift of Precambrian granite stretching from northern Colorado (NNW of Ft. Collins) to Casper, Wyoming, and bisected by the Laramie River.  The Park is best reached via Route 210, which leads north from Interstate 80 near the summit of the ridge and soon curves eastward through scenic terrain.

Deciding to escape the heat wave in Metro Denver, my wife and I drove up to Laramie today and then out to Curt Gowdy State Park.  Characterized by three reservoirs, rolling hills adorned with ponderosa pine parklands, scenic outcrops of granite and, in shaded canyons, pine-fir forest, the 3500 acre Park is popular for camping, hiking and fishing.  After stopping by the Visitor Center, we set off on the Crow Creek Trail, which leads upward through a beautiful canyon to Hidden Falls (4 miles roundtrip).  It is clearly the most popular hike at the Park but was not uncomfortably congested on this Tuesday afternoon; other than humans, we encountered mule deer, golden-mantled ground squirrels, red squirrels and a host of "Montane" songbirds.

In no hurry to return to 100 degree F temperatures along the Colorado Front Range, we have decided to visit Devils Tower tomorrow, a spectacular National Monument in northeast Wyoming that we have not yet had the pleasure to "closely encounter."  Details on that experience in the next post.

The Chorus of Summer

Here in the American Midwest, the hot, humid air of summer tends to suppress birdsong (as well as human activity); nevertheless, some distinctive sounds of the season persist: the croak of bullfrogs, the "fiddling" of crickets and the sharp "peent" of common nighthawks come to mind.

But the dominant chorus of summer is that of annual cicadas, echoing through the woodlands from mid July through early September.  While not nearly as abundant as periodic cicadas, which emerge in late spring every 13 or 17 years, the annual species can produce an annoying background din at times.

On the other hand, their chorus is nostalgic for those of us who grew up in cicada country and who would deny these insects their brief, noisy time in the sun?  Having spent several years underground as a grub, drawing nutrition from a tree root, they have but a couple weeks to mate and lay eggs before they die.  Besides, the heat-fueled cicada chorus indicates that summer is half over, a welcome sign for those of us who prefer cool weather.

Barry retests Human Folly

Approaching the Louisiana coast, Tropical Storm Barry will soon retest the folly of building a large city at the mouth of North America's largest river system, half below sea level and dependent on the protection of pumps and levees.  Up to 20 inches of rain is expected in some areas and the Mississippi River is already in flood stage.

Of course, New Orleans is not the only coastal American city to bloom around an early seafaring port but one would think that we have learned our lesson over the past 500 years.  Long enamored with the beauty and utility of rivers and the ocean, we humans can no longer fold up our tents or move to a higher cave when threatened by high water.  Even in the face of rising sea levels and destructive annual floods, many U.S. cities and towns stand their ground, determined to rebuild (with Federal assistance assured).

While port facilities and historic structures cannot or should not be moved, it is time for humans to abandon floodplains and high risk coastal areas.  If we do not initiate the process (while also doing what we can to mitigate global warming), nature will force our hand.

Another Try at Eagle Bluffs

Since I am back in Columbia, Missouri, for a week, I decided to visit Eagle Bluffs Conservation Area, hoping that the floodwaters had receded; alas, a sign on the entry road indicated a road closure ahead and, since I was driving our VW Beetle, I was forced to turn around within a few hundred yards.  A bald eagle, a few crows and a couple dozen horned larks were all that I encountered.

Returning to Route K, I decided to try the Buck and Katy Lakes portion of Eagle Bluffs, just south of McBaine.  There I was greeted by a lone scissor-tailed flycatcher on the power line and was pleased to find that the graveled roads were passable.  Killdeer, great egrets and red-winged blackbirds dominated the scene, joined by a few turkey vultures, great blue herons, tree swallows and spotted sandpipers.  Within a half-hour, I was back on the road.

No doubt, the severe flooding along the Missouri River will be slow to resolve, especially since heavy rains have fallen across its upper watershed in the past few days.  We could use some of that rain here in Central Missouri and expect thunderstorms this afternoon.

The Rivers of Illinois

Driving back to Missouri from a wedding in Cincinnati, my wife and I took the "southern route," coming across Interstate 64 from Louisville to St. Louis.  After crossing the broad Ohio River and undulating through the hills of the Hoosier National Forest, in southern Indiana, the highway enters relatively flat terrain north of Evansville and soon crosses the Wabash River to begin its trek across south-central Illinois; surprisingly, that 150 mile segment of the Interstate only crosses two rivers large enough to warrant highway signs, the Little Wabash in southeast Illinois and the Kaskaskia River in southwest Illinois, though a handful of creeks are also recognized.

Bordered on the west by the Mississippi and on the south by the Ohio, Illinois sends almost all of its water toward the Gulf of Mexico; while the Eastern Continental Divide passes through Chicago, canals link the Chicago and Calumet Rivers (which formerly emptied into Lake Michigan) with the Des Plaines River, which flows southward into the Illinois River, thus disrupting the Divide.  The latter river, formed by the convergence of the Fox, Des Plaines and Kankakee Rivers, drains a broad swath of the State, from its northeastern corner to the St. Louis area, where it empties into the Mississippi.  Northwest Illinois is drained by the Galena, Apple, Rock, Green and Edwards Rivers (north to south), all flowing westward to the Mississippi.  In west-central Illinois, the Vermillion River rises from several tributaries and then flows southeastward to the Wabash (the largest northern tributary of the Ohio), while the Kaskaskia begins its long journey southwestward to the Mississippi and the Little Wabash snakes southward to the Ohio.  Finally, the Big Muddy River and a host of smaller streams drain the Shawnee Hills of southern and southeastern Illinois, most flowing toward the Ohio River, itself a massive tributary of the Mississippi.

In landscapes with prominent ranges or dramatic relief, it is usually easy to visualize the component watersheds; but in a relatively flat expanse of terrain (which defines most of Illinois), one must pay close attention to subtle divides and maps to fully understand the regional hydrology.  Of course, the river networks of Illinois are, in large part, the product of glacial erosion and meltwater flow, acting on the underlying geology.

The Ridgecrest Earthquakes

The recent earthquakes near Ridgecrest, California, were unusual in a couple of ways.  The first, on July 4, was a 6.4 magnitude quake, while the second, a day later, was a 7.1 magnitude quake, some 11 times more powerful.  The initial earthquake has thus been categorized as a pre-shock, having occurred before a stronger one though both have been followed by numerous aftershocks; the first quake was centered 6.6 miles below the surface of the desert while the second was 4 miles deeper.

Well northeast of the San Andreas Fault, these strong earthquakes developed on two perpendicular fault lines that stretch beneath the Mojave Desert at the south end of the Owens Valley.  The latter runs NNW to SSE between the Sierra Batholith and the fault-block White Mountains Range of the western Great Basin; both of these ranges continue to rise and the crust of the Great Basin is under increasing tension (pulled apart in a West-East direction).

These earthquakes demonstrate the complexity of fault lines in Southern California, many of which are not completely mapped.  While the earthquakes occurred far from the San Andreas Fault (which will eventually deliver "The Big One") their occurrence may reflect increasing pressure within the latter Fault and their crustal movements may trigger additional earthquakes as pressure is transferred to other fault lines that crisscross the region.

See also: The Nature of Aftershocks and Earthquakes & Tectonic Plates

The Season of Acknowledgement

As we enter the heart of summer in the Northern Hemisphere, many of us will experience heat waves, severe storms, hurricanes, floods, drought, wildfires and water shortages, focusing our attention on the projected impact of global warming.  Even climate change deniers may be forced to acknowledge the reality of our predicament.

For all who care about the science of climatology and the impact of global warming on human populations, I recommend reading Welcome to Climate Change, the May/June, 2019 issue of MIT Technology Review.  Drawn to my attention by my son, the review covers efforts to reduce the severity of global warming, the various technological means of adapting to a warmer climate and the suffering (present and future) that has and will be borne (inequitably) by human societies.

No doubt, those who seek out and read this review will be those who are already alarmed by the potential impact of climate change and are doing their part to mitigate global warming; Trump and his legions will toss it in their collective barrel of fake news.  Fortunately, local governments, many countries, conservation organizations and an increasing number of small and large industries (that understand the economics of climate change and the importance of being on the right side of this issue) are adopting and promoting green technology despite the rhetoric and policies of the current American Administration.