Mother & Destroyer

The Sea is the mother of all life on Earth, which first evolved in her realm about 3.6 billion years ago.  It would not be until 450 million years ago that some species became terrestrial but a fabulous diversity of life still inhabits Mother Sea, much of which has yet to be discovered by humans.

Nourishing and sculpting terrestrial ecosystems with her weather systems, she also destroys habitats and human developments with coastal hurricanes, severe inland storms and flooding rains.  Indeed, as our climate warms, these destructive events will intensify.

Furthermore, as her component oceans open and close, earthquakes, tsunamis and volcanism alter terrestrial landscapes and destroy regional life; the recent earthquakes in Venezuela demonstrate a risk that stretches across the globe.  The Sea, an essential component of Life on Earth is both generous and destructive; we could not live without her but often succumb to her power.  

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

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

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 

Mesa de Maya

Just when I thought I had seen every landscape in Colorado, I caught sight of Mesa de Maya, northeast of Branson in southeastern Colorado.  This massive tableland, rising above the surrounding grasslands is part of the Raton-Clayton Volcanic Shield; in fact, it is contiguous with Black Mesa, in the Oklahoma Panhandle, that I discussed earlier this week.

Like all mesas in this Volcanic Shield, Mesa de Maya is an erosional remnant, protected by a thick cap of basalt.  Its elevation is 6900 feet in Colorado, declining to 4900 feet in Oklahoma.  Northern portions of the Mesa drain to the Purgatoire River (a tributary of the Arkansas River) while the southwest portion drains toward the Dry Cimarron River, in northeast New Mexico, and the southeast portion is drained by tributaries of North Carrizo Creek (itself a tributary of the Cimarron).

The thin soil atop Mesa de Maya supports a grassland ecosystem while its flanks are covered by a mixed woodland of juniper and piñon pine.  Unfortunately, almost all of the Mesa is privately owned ranchland, not accessible to the public.  Nevertheless, we can certainly appreciate its grandeur from afar. 

Black Mesa and Beyond

Early this morning, we left Guymon and traveled to the northwest corner of Oklahoma's Panhandle.  Our first stop was at Black Mesa State Park, where we enjoyed a hike along the rim of a scenic canyon.  Bird sightings included sharp-tailed grouse and green-tailed towhees, among more common species; mule deer and pronghorn were also observed.

About ten miles northwest of the State Park is Black Mesa itself, named for its cap of basalt; indeed, this massive tableland represents the eastern end of the Raton-Clayton Volcanic Field.  Rising to 4974 feet, Black Mesa is the highest summit in Oklahoma.  Though we did not have the time nor the energy to climb its wall, we did hike through protected lands just north of the Mesa.

The Upper Cimarron River flows past the southern base of Black Mesa and we followed it westward and upward toward its source in northeastern New Mexico; there it is known as the Dry Cimarron River to distinguish it from the State's other Cimarron River which heads in the Sangre de Cristo Mountains and is a tributary of the Canadian River.  Approaching the headwaters of the Dry Cimarron, bordered by towering mesas, we elected to divert northward into Colorado.  After crossing a low pass, we could see the snow-covered Culebra Range and Spanish Peaks to the west, assuring us that we were nearly home.

Flashback Post XXXVI

Mauna Loa, the largest active volcano on Earth, has reawakened on the Big Island of Hawaii.  A post from 2007 explains the formation and probable future of that volcanic island chain.

See: The Hawaiian Ridge 

Tonga Volcanism

Today, a powerful volcanic eruption in the Tonga archipelago set off tsunami advisories across the Pacific Ocean, including the West Coast of the U.S.  As I write this blog, it is too early to know if any effects will be observed in our country.

The islands of Tonga, numbering 170, lie in the southwest Pacific Ocean and are grouped in two parallel chains that trend north to south.  The chains are divided by the Tonga Trench, where the Pacific Plate is dipping beneath the Australian Plate.  Islands of the western chain are the product of subduction volcanism; the leading edge of the subducting Pacific Plate melts as it approaches the mantle, igniting the volcanoes that form the western chain.  This morning's eruption was of a volcano that had not yet risen above sea level (it had not yet produced a visible island).

The eastern chain of the Tonga archipelago does not include active volcanoes since they do not lie over a volcanic hotspot, an active oceanic ridge or along a subduction zone.  However, some of these islands contain volcanic rock from the Eocene Period (50 million years ago); the ancient volcanoes formed elsewhere and traveled westward on the Pacific Plate. 

Canary Islands Volcanism

 The Canary Islands are a chain of seven volcanic islands that stretch ENE to WSW off the northwest coast of Africa.  Like the Hawaiian Islands, they have formed over an oceanic hotspot.

As the Atlantic Ocean opened and the Tethys Sea closed, the African Plate has moved to the ENE, passing over the hotspot (an upward plume of the Earth's mantle).  The oldest of the Canary Islands are thus at the northeast end of the chain and are now devoid of active volcanism (i.e. they are in the erosional phase of their natural history).  The middle islands of the archipelago now lie northeast of the hotspot and are unlikely to experience active volcanism.  The southwestern islands, including La Palma, sit above the hotspot and, as we have seen this week, are prone to volcanic eruptions.

The current eruption and basalt flows on La Palma could last for months, if not longer.  After all, the eruption of Kilauea, on the Big Island of Hawaii, has continued since 1983.

Back in the Air

For the first time since the pandemic began, I boarded a flight yesterday.  Headed for Denver from Columbia, I was required to change planes in Dallas, Texas, where, unfortunately, a cluster of persistent thunderstorms closed the airport for almost three hours.

Finally able to depart, we headed northwest to Denver.  In the wake of the storms, clear skies prevailed and I was treated to sweeping views of the Southern Plains and Western High Plains.  Across Northern Texas and the Panhandle of Oklahoma, a series of rivers cut through the dry landscape, all flowing southeastward toward the Gulf of Mexico.  At the Tristate of New Mexico, Oklahoma and Colorado, outcrops of volcanic basalt adorned the surface of the Raton Mesa; beyond this broad ridge the terrain dropped into the Arkansas River Valley of Southeastern Colorado where a mosaic of crop fields bordered the stream.  Farther north, as the Front Range Peaks came into view, we flew above the pine-studded Palmer Divide and descended into DIA.

After more than a year on the ground, it was a pleasure to view our planet from a plane once again.  While the varied ecosystems and their residents may lie far below, too distant to fully appreciate, their interconnection is especially evident from 30,000 feet. 

St. Vincent's Volcano

St. Vincent is an island near the southern end of the Lesser Antilles, a tropical archipelago that lies along the eastern edge of the Caribbean Plate.  These islands are volcanic in origin, produced by the subduction of the American Plates beneath the Caribbean Plate as the Atlantic Ocean continues to open.

La Soufriere is a volcano that forms the northern half of St. Vincent Island.  Geologic studies indicate that the volcano has developed over the past 600,000 years, including six major eruptions since 1718; the last of these began on April 9 and may continue for weeks (if not longer).  Toxic, volcanic ash is currently falling across the island.

Most of the beautiful, tropical islands on our planet are volcanic in origin and many remain active or, at best, dormant.  Those who live on or visit these parcels of paradise must accept the risk of eruptions, however infrequent they may occur.

The Alborz Mountains

While watching Tehran, a miniseries on Apple TV (which I recommend), one repeatedly sees the majestic mountain wall just north of the city.  These are the Alborz Mountains and the snowy massif near Tehran is Tochal, elevation 13,005 feet.

Wrapped along the southwest and southern coasts of the Caspian Sea, the Alborz Range crumpled up during the mid-late Tertiary Period as the Tethys Sea closed and the Arabian Plate collided with the Eurasian Plate, a process that continues today.  In concert with that uplift, volcanism occurred in some areas and Mt. Damavand, northeast of Tehran, is a volcanic cone that rises to 18,406 feet, the highest point in the Middle East.

Though less famous than the Alps and the Himalayas, the geologic and natural history of the Alborz Mountains is very similar; indeed, they are one of multiple smaller ranges that connect the Alps and Himalayas, creating a mountain corridor from France to Southeast Asia.

Geologic History of Scotland

In the late Precambrian Era and into the Cambrian Period, the basement rock of Scotland was part of proto-North America, having accreted to that Continent as a series of exotic terranes.  The Iapetus Ocean separated this continental mass from that of England and Western Europe.

Then, about 450 million years ago (MYA), the Iapetus Ocean closed and the two continents collided, triggering the Caledonian Orogeny; much later, about 150 MYA, the Atlantic Ocean opened and Scotland remained with Europe.  Today, ancient rocks that preceded the Caledonian Orogeny underlie most of Scotland but surface primarily across the Western Islands and the Highlands; the latter region is divided into the Northwest Highlands and the Grampian Mountains by the Great Glen Fault.  As these Highlands crumpled upward, volcanism, erosion and displacement of emplaced metamorphic crust produced the complicated geology of that region.  South of the Highlands Boundary Fault, the Central Lowlands represent a Rift Valley, characterized by Paleozoic sediments, volcanic intrusions and more recent glacial deposits.  Finally, the Southern Uplands, bordering England, are comprised of uplifted and eroded Silurian crust from the Iapetus Ocean.

Acting on this underlying mosaic of Precambrian and Paleozoic bedrock, the Pleistocene Glaciers (1.8 million to 10 thousand years ago) plowed down the higher peaks, gouged out canyons and valleys and then left behind layers of till as they receded northward.  In addition, their meltwaters scoured the terrain and rising seas drowned the coastline, separating the western and northern islands from the Scottish mainland. 

Above the Cascades & Great Basin

Flying back to Denver, yesterday, we changed planes in Seattle.  On that second flight, we took off to the south, soon passing the massive bulk of Mt. Ranier, to our east.  Curving southeastward, we then caught sight of the remnant cone of Mt. St. Helens to our southwest and, within a few minutes, flew over the snowy crest of Mt. Adams.  Next came the distinctive form of Mt. Hood, across the Columbia River Valley, and other prominent summits farther south; unfortunately, haze obscured the distant horizon and I was unable to locate Mt. Shasta, in Northern California.

Having formed over the past 36 million years, as the Farallon and its remnant Juan de Fuca Plate have been subducting beneath the North American Plate, the Cascades stretch from west-central Washington to Northern California and continue to form today.  Indeed, many Cascade volcanoes have developed and eroded (or exploded) away during that time and the prominent volcanic peaks mentioned above are less than 2 million years old; the eruption of Mt. St. Helens, in 1980, was a clear indication that the range is still evolving.

East of the Cascades, is the high, dry desert of the Great Basin, stretching from eastern Oregon and California across Nevada, southernmost Idaho and western Utah.  Fault-block ranges, running north to south, are separated by broad valleys which harbor sage grasslands, seasonal rivers, sinks, ephemeral lakes and a few large saline lakes. Unfortunately, clouds obscured the mountains of Utah and Colorado until we crossed the Front Range above Rocky Mountain National Park and descended into Metro Denver.

Northwest to Ketchikan

Escaping the latest heat wave along the Colorado Front Range, my wife and I will be visiting friends in Ketchikan, Alaska, over the next several days.  There we will enjoy afternoon highs in the 60s (F) and overnight lows in the 50s; of course, rain showers are also in the forecast, as one might expect in Southeast Alaska.

As I discussed in Alaska's Collage of Terranes, most of the State is a mosaic of exotic terranes and volcanic island arcs, later molded by glaciers, earthquakes, volcanic eruptions, torrents of meltwater and fluctuating sea levels.  Ketchikan sits in the Gravina Belt, composed of mid Jurassic to early Cenozoic volcanic rocks, sandwiched between the Alexander Terrane, to the west, and the Stikine Terrane, to the east.  The Alexander Terrane is especially interesting; its Silurian and Devonian strata and their cargo of fossils indicate that it was torn away from Siberia as the Northern Pacific opened.  The Stikine Terrane, on the other hand, formed as a volcanic island arc from the late Paleozoic Era into the early Mesozoic.

Today, Ketchikan, sitting on the Inside Passage, is a cruise ship port during the summer months.  Having limited time for our journey, we will be flying from Denver (with a plane change in Seattle).  More on our adventure in upcoming posts.

Guatemala's Volcanic Eruption

The eruption of a volcano in Guatemala and its tragic consequences have drawn attention across the globe this week.  Some will blame the event on the random violence of nature while others will see the hand of God in the destruction and suffering.  But if you must accuse someone or something, blame the Atlantic Ocean.

During the Permian Period, some 250 million years ago (MYA), the Continents had merged to form Pangea.  By the Triassic, about 200 MYA, the Tethys Sea opened, separating Laurasia (the northern Continents) from Gondwanaland (the southern Continents).  Then, during the Jurassic Period (some 150 MYA), the Atlantic began to open and the American Continents were pushed westward, a process that continues today.  In concert, the oceanic Farallon Plate was forced to subduct beneath the advancing Continental Plates; today, the Juan de Fuca Plate (in the Pacific Northwest), the Cocos Plate (west of Mexico and Central America) and the Nazca Plate (west of South America) are the primary remnants of the Farallon Plate and all continue to subduct beneath the American Plates.

As these oceanic plates subduct, their leading edge melts when it approaches the Earth's mantle, triggering the formation of volcanoes (the Cascades, the western mountains of Mexico and Central America, and the Andes); earthquakes and tsunamis also result from this tectonic activity.  The current eruption in Guatemala, releasing volcanic ash, pyroclastic flows and lahars, is thus a secondary effect of the Atlantic's expansion.  Earth did not stop evolving when we humans appeared!

The Korean Peninsula

In light of the ongoing Olympics, I thought I might take a look at the geography of the Korean Peninsula.  Extending southward from northeastern China and extreme southeastern Russia, the Korean Peninsula separates the Sea of Japan, to its east, from the Yellow Sea, to its west.  More than 65% of the Peninsula is covered by mountainous terrain, primarily across its northern and eastern regions.  Most of the ranges are composed of Precambrian igneous and metamorphic rock though some areas of volcanism exist as well.  Paektusan, just over 9000 feet, is the highest summit on the Peninsula, rising along the border of China and North Korea; it is known for it large caldera (created by a massive eruption in 946 AD) which holds Heaven's Lake.

Three major rivers drain most of the Korean Peninsula: the Nakdong flows southward through its southeastern region, the Han River flows westward through the central portion of the Peninsula (passing through Seoul) and the Taedong River flows southwestward through the northern Peninsula, passing through Pyongyang.  More than 3500 islands and islets rise off the western and southern coasts of the Peninsula, including Jeju, a large volcanic island in the Korean Strait (south of the Peninsula) which was formed by Hallasan (6398 feet), a large shield volcano that is the highest peak in South Korea.

While the Korean Peninsula extends across the same latitudes as Japan, it does not enjoy the warming effects of the Japan Current and its continental climate is considerably colder.  PyeongChang County, which is hosting the 2018 Winter Olympics, is about 78 miles east of Seoul.

Four Valleys in New Mexico

Yesterday morning, I left Roswell (in the Pecos River Valley) and drove west on Highway 380.  Climbing toward the Sacramento Mountains, I left the desert and soon reached grass-covered hills, passing Capitan Peak (10,083 feet) to my north.  The highway then entered steep-wall canyons before offering a spectacular view of Sierra Blanca (11,973 feet), the crest of the Sacramento Range.

At the Indian Divide, I left the Pecos River watershed and dropped into the Tularosa Basin, famous for White Sands National Monument and the massive Carrizozo basalt flow (5000 years old).  Highway 380 crosses the latter and several pull-offs are provided for close observation of this interesting volcanic landscape.  After climbing the Oscura Mountains, the road then drops into the Jornada del Muerto (Day of Death) which I hastened to cross.  A long, slow climb from there took me to the east wall of the Rio Grande Rift, lined with fault-block ranges, laccoliths and volcanic domes.

After descending to the valley floor and crossing the Rio Grande River, I took the opportunity to visit Bosque del Apache NWR, a renowned birding site, 8 miles south of San Antonio, New Mexico.  There I saw large flocks of snow geese, a fabulous diversity of waterfowl, bald eagles and, yes indeed, thousands of sandhill cranes! (See the last few posts).

Eruption of Mount Agung

Mount Agung, 9944 feet, is in western Bali.  One of 78 active volcanoes in Indonesia, its last major eruption occurred in 1963 but another is expected within the next few weeks.  Earthquakes developed on and near the volcano back in September and the release of smoke and ash has been intermittent throughout October and November.

The volcanic islands along the western and southern edge of Indonesia have formed as the Indo-Australian Plate has been subducting beneath a southeastern extension of the Eurasian Plate.  As it is forced downward, toward the Earth's mantle, the leading edge of the subducting plate melts and plumes of magma push up through the crust of the overriding plate.  Initially producing a volcanic island arc, the ongoing subduction and volcanism has culminated in the large islands that we observe today (Sumatra, Java, Bali and others to their east).

Another major eruption of Mount Agung will likely produce widespread devastation but will not come close to the effects of Mount Toba's eruption, on Sumatra.  That supervolcanic eruption, which occurred 74,000 years ago, temporarily cooled the Earth's climate and had a major impact on the human population of our planet; indeed, a significant percentage of early humans had left Africa and colonized the southern rim of Asia by that time (see The Toba Winter).

Mexico's Subduction Quake

While the attention of most North Americans has been focused on Hurricane Irma, about to unleash her fury on Florida, a strong earthquake struck off the Pacific Coast of southern Mexico yesterday.  The magnitude 8.2 quake occurred along a subduction zone, where the Cocos Plate (a remnant of the massive Farallon Plate) is dipping beneath the North American Plate; unfortunately, at least 58 persons were killed by the earthquake.

In such subduction zones, the edge of the over-riding plate is pulled down by friction with the subducting plate.  Eventually, this edge rebounds upward, displacing a massive amount of seawater and often triggering a tsunami.  Fortunately, in this case, the latter did not develop.

As the North and South American Plates continue to drift westward in concert with the opening of the Atlantic Ocean, subduction of the Farallon remnants (the Juan de Fuca, Cocos and Nazca Plates, north to south) will continue, igniting volcanic ranges (the Cascades, Mexican volcanoes, Central American volcanoes and the Andes) as they melt and triggering earthquakes offshore that spread across the mainland.