Flashback Post LXIX

Yesterday's Magnitude 8.8 earthquake, off the coast of eastern Russia's Kamchatka Peninsula, was the 6th most powerful quake ever recorded.  Geologically speaking, it occurred along a subduction zone, triggering a tsunami warning across the Pacific Ocean.  A post from April of 2009 explained this phenomenon.

See: Tsunamis and Subduction Zones 

Flashback Post LXVII

Mt. Etna is erupting once again and will continue to do so in the future.  A post from August of 2011 discusses the volcano's geology.

See: Geology of Mt. Etna

Shawnee Hills Highlights

Today, we explored a swath of the Shawnee Hills, southeast of Marion, Illinois.  Rather than describe the adventure in detail, I have decided to offer a few photos that depict the geography of that region.  These landforms reflect the cap of Carboniferous sandstone that lies across the region and the erosive forces that have been active for millions of years (especially during the Pleistocene).

As is usually the case, I enjoyed the journey as much (if not more) as the destinations.  To paraphrase James Taylor, "It's enough to cover ground.  It's enough to be on your way."

Sand Cave:

Jackson Falls:

Fern Clyffe State Park:

The Myanmar Earthquake

The tragic, 7.7 magnitude earthquake in Myanmar this week occurred along fault lines between the Indian and Eurasian Plates.  The former continues to push NNE into the latter, forcing up the Himalayas and producing frequent earthquakes in that area.  Adding to tectonic pressure within that region is the subduction of the Indo-Australian Plate beneath the southeast portion of the Eurasian Plate.

While these powerful earthquakes seem to have a predilection for impoverished countries, where the houses and buildings do not meet modern codes, this is a false narrative.  That assumption is derived from the fact that much of the planet remains relatively "underdeveloped."  Of course, our brief time on Earth also fosters that conclusion.

Here in the U.S., most quakes have been relatively mild over the past Century but major, destructive events lie ahead, especially along the West Coast (an Active Margin).  We can contribute to relief efforts and, perhaps, improve our quake prediction accuracy but we will never control tectonic activity. 

A Walk in the Foothills

On this mild, sunny morning, my wife and I headed up to South Valley Park, in the lower foothills of southwest Metro Denver.  Characterized by open grasslands that stretch along and between outcrops of the Lyons Formation (Permian Period) and the Fountain Formation (Pennsylvanian Period).  A fine network of trails offers scenic views of the Park and of the higher foothills to the west.

Elk often winter in this valley but this morning's mammal sightings were limited to mule deer and rock squirrels.  Scrub jays, spotted towhees and magpies were common and we also encountered blue jays, Steller's jays and a lone red-tailed hawk; prairie falcons may also be observed at this Park, nesting on the higher rock outcrops.

Due to the spectacular scenery, fine trails, interesting wildlife and easy access from the city, this refuge can be crowded, especially on weekends.  I thus recommend an early morning, weekday visit if possible. 

The Short Life of Lake Powell

Named for John Wesley Powell, a geologist who explored the Green and Colorado Rivers for the U.S. in 1869, Lake Powell filled Glen Canyon after construction of the Glen Canyon Dam in the early 1960s.  Opposed by environmentalists, including Edward Abbey, the Dam was built for water storage, hydroelectric power and recreation.

After reaching a maximum volume in 1983, the reservoir began to shrink in the late 1990s as climate change reduced mountain snowpack and increased evaporation.  In concert, sedimentation from the Colorado and San Juan Rivers was filling its basin from below.  As the lake level continues to fall and the upper feeder streams resurface, energy production will cease and Lake Powell will reach the "dead pool" state. Unfortunately, since adequate deep release tunnels were not included in the dam's design, flow through the Grand Canyon (just downstream) will be greatly diminished.  A current proposal, not yet fully endorsed, is to create new channels through the adjacent bedrock before sediment fills Glen Canyon and its riverine ecosystem is forever degraded.

For a concise and readable history of this saga, I strongly recommend Life after Dead Pool, by Zak Podmore (the source for this post).  He deftly weaves the political, industrial, hydrologic, cultural, geological and ecological elements of the Lake Powell debacle.  My thanks to a good friend for introducing me to this fascinating book.  

The Erosive Force of Water

Beyond their stark beauty, the Faroe Islands demonstrate the erosive force of flowing water.  Since rifting from Greenland, 55 million years ago, this volcanic terrane has been molded by glacial ice, torrential rain, pounding waves, strong currents and numerous streams.  Due to their northern latitude, freeze-thaw cycles have also played a significant role in sculpting the islands.

Of course, most of this erosive activity persists today and is readily evident to the visitor.  Landslide scars are observed, frequent rain drenches the highlands, currents alter the course of boat transportation and powerful waves lash the rocky headlands.  Sheep and hares, both introduced by humans, are the only mammals that inhabit the steep, grass-covered slopes and countless waterfalls adorn the ridges.

This is a country of rock and water.  Though man has managed to settle along its coasts and fjords, water will eventually erode these scenic islands into the sea. 

Flashback Post LVI

Yesterday's hydrothermal explosion at Yellowstone National Park, while a threat to nearby humans and wildlife, does not begin to match the eventual volcanic eruption that threatens the region and, potentially, the planet.

See: The Yellowstone Time Bomb

Crossing Glacial Landscapes

Returning to Missouri from Northeast Ohio, we crossed a series of glacial landscapes.  While the term "glacial terrain" brings to mind rivers of ice, carving mountains or calving into the sea, past glacial effects are not as evident to the casual traveler.

Having spent a week atop the glaciated region of the Appalachian Plateau, we initially dropped onto the vast Lake Plain of Northern Ohio, the product of Pleistocene glacial erosion and a post-glacial meltwater lake (Lake Warren, the much larger predecessor of Lake Erie).  Angling southwestward  through Northeast Indiana, we soon passed the site of The Maumee Torrent, which marked the birth of the Wabash River Valley.

The remainder of our journey was across the Glaciated Plain of the Midwest, where the Pleistocene glaciers pushed southward, flattening the terrain.  As they retreated, they enriched the soil with glacial till, setting the stage for prairie ecosystems that have since given way to crop fields and cattle ranches.  Of course, the massive sheets of ice also determined the course of the Ohio, Mississippi and Missouri Rivers, which now drain the central U.S., from the Rockies to the Appalachians.

 

Back with the Martins

We have returned to my wife's family cottage on Sandy Lake, a small kettle lake on the Glaciated Plateau of Northeast Ohio.  During the summer months, this peaceful location is dominated by a large flock of purple martins that occupy a collection of apartments near the shore.

Noisy and active, the martins spend most of their day strafing the lake's surface for insects.  There they are often joined by a handful of cormorants, cruising about the calm waters or diving for fish, and by a pair of osprey that soar overhead before plunging into the lake to snare their prey.  Flocks of Canada geese and mallards forage along the marshy shoreline while a belted kingfisher moves among the docks, searching for schools of fingerlings.

This lakeside retreat is a pleasant escape from the summer heat that ravages most of the country.  Indeed, many climatologists believe that the Great Lakes region will be least affected by our warming climate (with the probable exception of heavy, lake-effect snowstorms).  Time will tell but, for now, we'll visit when we can.

New Jersey's Earthquake

The Magnitude 4.8 earthquake near Whitehouse Station, New Jersey, on April 5, was caused by a rather shallow, intra-plate slip along an old fault.  Though not uncommon in the Eastern and Central U.S., any quake not along the Pacific Coast garners significant attention.

Indeed, major earthquakes in North America generally occur along the Continent's Pacific edge where remnants of the Farallon Plate are subducting beneath the North American Plate or (in Southern California) where the Pacific Plate is sliding past the North American Plate.  The North American Plate, itself, is forming along the mid-Atlantic Ridge and is thus creeping westward; the Eastern Coast of the U.S. is a Passive Margin, defined primarily by the level of the sea.

Nevertheless, old fractures, faults and sutures remain beneath that region, having formed when the Appalachians rose or when our Continent formed from smaller fragments of crust.  When pressure builds, likely from geologic events along the Pacific Coast, these old joints may slip or rupture, producing an earthquake and its subsequent aftershocks.

   

Flashback Post XLVII

Yesterday's powerful earthquake on the west coast of Japan was a consequence of that country's complex tectonic structure, a subject discussed in a post back in September of 2008.

See: Earthquake Central

Flashback Post XLVI

Icelandic volcanism is back in the news due to current eruptions on that island.  The geologic/tectonic cause for this volcanic activity was discussed in a post back in March of 2010.

See: Iceland & Rift Volcanism 

The New River

Last October, while traveling through the Blue Ridge Mountains, I was fortunate to encounter the North and South Branches of the New River in northwest North Carolina.  The New River is actually quite old, perhaps the oldest river in North America.

From the junction of its two branches in North Carolina, the New River drops into the Ridge and Valley Province of the Appalachians, flowing northeastward.  Near Radford, Virginia, the river angles to the NNW, slicing through the Appalachian Plateau of West Virginia and eventually merging with the Gauley River to form the Kanawha River, a major tributary of the Ohio.  Having completed my medical residency at West Virginia University, in Morgantown, I was fortunate to experience a couple of canoe trips on the New River back in the late Seventies.

Geologists know this ancient river as the Teays, the predecessor of the Ohio River.  Before the glacial advances of the Pleistocene, the Teays (now the New, Kanawha and central Ohio Rivers) continued to flow northwestward across Ohio and northern Indiana, eventually entering the Upper Mississippi.  When the Pleistocene ice sheets blocked that course, the Teays diverted southwestward, forming the current Ohio River Valley.  See: From Teays to Ohio 

Flashback Post XLV

Today, on a flight from Dallas to Denver, I noticed mounds of rock rising from the rolling terrain of Southwestern Oklahoma.  They were the Wichita Mountains that I wrote about back in December of 2011 but, until today, had never seen.  A visit at ground level is in order.

See: The Wichita Mountains 

Bras d'Or Lake

Bras d'Or Lake (photo) is actually a large, multi-armed estuary in central Cape Breton Island that has two natural connections to the Atlantic Ocean at its northeastern extent.  Though several rivers and numerous creeks drain into the "lake," it is subject to tidal flow and thus has brackish water.  A man-made canal, used to facilitate shipping, also connects Bras d'Or Lake to the ocean at its southeastern end.

Almost 1100 square kilometers in size, the estuary is bordered by glacial drumlins in its northwestern region.  The variable salinity of its water greatly augments the diversity of its wetlands and resident wildlife and its varied ecosystem has received designation as a UNESCO Biosphere Preserve.

While our exposure to Bras d"Or Lake was strictly from adjacent roadways, knowing that this vast estuary is being protected for the welfare of our planet and the benefit of future generations was rewarding enough. 

East to the Adirondacks

Leaving Watertown, New York, this morning, we followed the Black River Valley eastward to Carthage.  There, Route 3 angles to the northeast, headed for Adirondacks Park, the landscape of which has been sculpted from a Precambrian Dome by glaciers and streams.

Our first adventure in that magnificent Park was a hike up Mount Arab (summit elevation 2533 feet), which offers a broad view (photo) of distant peaks and lakes.  Though the trail is officially only a mile in length, it is mostly a well-engineered stairway of rocks.

Having survived that ordeal, we headed to Lake Placid, where we will spend the next two nights.  Another hike is planned for tomorrow (if we can move in the morning). 

Nova Scotia Bound

After attending a family wedding in Cincinnati, my wife and I set off for Nova Scotia today, heading northeastward through Ohio, crossing the northwest tip of Pennsylvania and then driving eastward through New York.  There we will visit the Adirondacks and the Thousand Islands region of the St. Lawrence River and then cross northern New England.

In eastern Maine, we plan to wind up the Atlantic Coast before entering Canada.  Much of our road trip will involve a journey through southern New Brunswick, Nova Scotia, Cape Breton Island and Prince Edward Island, all new territory for me.

Our first stop was at Letchworth State Park, in western New York, which harbors "The Grand Canyon of the East."  To be more specific, this scenic gorge (see photo) was sculpted by the Genesee River as it flows NNE from northwestern Pennsylvania to Lake Ontario at Rochester.  The walls of the gorge are composed of Carboniferous and Devonian strata of the Appalachian Plateau.  Three scenic waterfalls along the Genesee also grace the Park.  More details on our road trip over the next two weeks.

Addendum: Hurricane Lee may alter our plans; stay tuned.  

Morocco's Earthquake

A magnitude 6.8 earthquake struck in the Atlas Mountains, southwest of Marrakesh, yesterday, killing more than 800 people.  The quake occurred along one of many faults within the range, which stretches northeastward from the Atlantic coast and has peaks that exceed 13,000 feet.

The Atlas Mountains initially formed as a fault-block range during the Jurassic Period, when the regional crust was thinning as Pangea continued to rift apart.  Later, early in the Cenozoic Era (about 65 million years ago), additional. uplift was produced by the collision of the African and Eurasian Plates.

While these mountains lie well south of that collision zone, Africa is still moving to the NNW as the Atlantic and Indian Oceans continue to open; in addition, the East African Rift is gradually splitting the Continent.  These major tectonic processes increase pressure on faults throughout Africa, producing earthquakes when they slip or rupture.

Addendum (9/11/23): The death toll has now exceeded 2800 individuals 

Detoured in Kansas

Heading back to Colorado yesterday, I was forced to leave Interstate 70 at Salina, Kansas, due to a serious accident west of that city.  Generally familiar with the regional landscape, I drove north to Kansas Route 18 and continued westward.  Though I had never taken that road, I knew it would cross the northern portion of the Smoky Hills.

It turned out to be a pleasant, uncrowded drive across scenic terrain.  Cattle ranches covered much of the area, where rock fence posts and old rock houses attest to the regional geology (see  Post Rock Country).  A number of sculptures, apparently constructed with old tractor parts, also adorned the route, most depicting dragons or dinosaurs.  Birdlife was typical of the Great Plains, dominated by turkey vultures, mourning doves, western kingbirds and massive flocks of cliff swallows; common nighthawks were also observed on that hot, sunny afternoon, apparently refueling after their long migration.

At Plainville, I turned south toward Hays (where I spent the night).  En route, I crossed the broad valley of the Saline River and kept an eye on thunderstorms, forming to the northwest.  While the accident was certainly unfortunate for those involved, it forced me to explore new and interesting geography.