California's Cascade Volcanoes: Medicine Lake Highland & Lava Beds National Monument

Medicine Lake Highland is a massive shield-like volcano in Northern California, east of Mount Shasta in a region that combines features of the Cascades with those of the Modoc Plateau and Basin and Range provinces.  The volcano has a volume of 130 cubic miles, making it California's largest volcano.  And most people have never even heard of it!  The volcano rises nearly 4,000 feet above the Modoc Plateau, from a starting elevation of roughly 4,000 feet to nearly 8,000 feet at its summit.  The Medicine Lake Highlands span about 30 miles north-south, and 20 miles east-west. 
Looking southwest, across Lava Beds National Monument, toward the massive shield edifice of Medicine Lake Highland.
On my recent geology field studies trip, offered through Modesto Junior College (taking extra classes purely for the joy of learning seems to be a sort of hobby of mine), I had the privilege of traveling to Lava Beds National Monument to see the products of the Medicine Lake volcano - specifically, lava flows and lava tubes. 

Basalt lava flows in the foreground, with the lava source, the Medicine Lake shield volcano, in the background.
After our stay at Lava Beds, we drove up and over the Highlands, traversing its length to experience Mammoth Crater, the source of 70% of the lava flows in Lava Beds National Monument, and the caldera at the summit which contains the beautiful Medicine Lake itself.
Mammoth Crater, 350 feet deep and a quarter-mile wide, is a large vent on the flank of Medicine Lake Highland.

Lava Beds National Monument contains miles and miles of cave systems, lava tubes that formed as channels of lava cooled from the outside.  As the top, sides, and bottom of a lava flow cooled, it hardened into a crust, allowing hot, fluid lava inside to continue to flow and drain out, leaving behind a hollow tube, or cave. 
Opening of a lava tube, or cave.
Some features inside lava tubes are similar to those found in more familiar limestone caves, but instead of being formed as dripping water leaves behind mineral deposits, formations like "lavacicles" were formed as lava dripped from the ceiling as a tube cooled.  Access to lava tube caves is gained when a portion of the roof collapses, providing an opening to the chamber below. 
Entering Skull Cave
Lava Beds National Monument is home to 14 species of bats.  Many are permanent residents, choosing from a variety of habitats in the monument, from miles of caves, to cliff faces and even trees; but some species migrate here from Mexico or as far south as South America.  The bats at Lava Beds are insectivores, catching flying insects using echolocation.  I was thrilled to stumble upon a few bats in the darkness of one cave; I don't know what species they were, but according to the National Park Service, the most common type seen in the lava tubes is Townsend's Big-eared Bat (Corynorhinus townsendii). 

The best thing to do if you come across bats is observe them quietly and respectfully for a moment if you'd like, then leave them in peace.  Don't shine your flashlight directly at them, and be very quiet.  Do not try to touch them; don't make too much noise or disturb them in any other way!

Bats are fascinating animals, and a valuable part of the ecosystem; I'm afraid they are too often underestimated.  We should be thankful for the insect control service they provide, eating up to their body weight in insects each night!  Humans have absolutely NO reason to fear bats or cause them any harm.

A good portion of our time at Lava Beds was spent exploring these fascinating caves, wearing protective clothing (basalt is sharp!) as well as helmets and headlamps for all those dark passages and tight squeezes! 
A very happy naturalist, delving into the realms of geology and caving.
An interesting fact about the Medicine Lake shield volcano (or, more accurately, "shield-like" volcano) is that it exhibits bimodal volcanism.  This means that it has more than one magma chamber, with more than one magma type; in addition to erupting basalt lava, from magma chambers of basaltic magma, it also erupts rhyolite lava from separate magma chambers.  Evidence of this bimodal volcanism can be seen at Glass Mountain, a fairly young (900-year-old) rhyolitic plug dome on the southwest flank of the Medicine Lake Highlands.  And as you may already know, rhyolite lava, when it cools extremely quickly, forms beautiful smooth, black volcanic glass: obsidian.  When that same lava mixes with gases, it forms the feather-light, frothy pumice.  Both can be found side-by-side at Glass Mountain.
Obsidian at Glass Mountain
At the summit of Medicine Lake Highland is a large 4-mile by 6-mile caldera, formed after the collapse of the volcano's summit 100,000 years ago.  The Highlands were glaciated at one point after this, and through their slow grinding processes, the glaciers created enough glacial clay to essentially seal up the caldera.  This layer of impervious clay prevented water from seeping into the porous basalt as it does in the rest of the Highlands and Lava Beds areas, and allowed the formation of a lovely subalpine lake.  Medicine Lake, as it is called, is a shallow lake of extremely cold water, and is a welcome sight to wildlife and travelers alike after traversing miles of lava flows.
Medicine Lake
 


Comments

Post a Comment

You Might Also Like:

Birds of the Desert: Residents & Spring Migrants

Image
Nearly everyone knows the desert as a barren, desolate land of extremes: high heat, low precipitation; little available food and water; prickly, spiny, unfriendly plants growing in a sea of rocks and sand as far as the eye can see.  But for those who stop and look closer, the desert reveals itself as the beautiful, incredible, mesmerizing place it truly is, teeming with unexpected life. Juvenile male Costa's Hummingbird visiting chuparosa blooms next to our campsite in Anza-Borrego Desert State Park. I particularly love the desert in the spring, when the annual wildflowers, cacti, flowering trees and shrubs are all in bloom.  (I've experienced the desert in the searing 120 degree heat of summer, and the rainy, even snowy cold of winter... and spring wins every time!)  Eric and I just returned from a week in the Colorado desert, exploring the imperiled, accidental Salton Sea (more on that coming soon), the vital wetlands of the Sonny Bono Salton Sea National Wildlife Refu
Read more

A Shorebird Primer: Godwits, Curlews, Willets and Whimbrels

Image
For those of us living in the Great Central Valley, autumn is the time to head to the coast.  Of course, there is no bad time to visit California's magnificent coastline.  But as the heat and haze of summer drag on in the Valley, the sea becomes increasingly tantalizing: September and the onset of autumn bring sunny weather and an abundance of migratory seabirds and shorebirds to our coast. A new birder visiting California's Central Coast will undoubtedly be met with a splendid array of very confusing birds.  Among these are small shorebirds like  "peeps" (sandpipers), Sanderlings and various  plovers .  But the larger birds can be just as confusing, until you learn a few distinguishing features.  Four large shorebirds that are commonly seen (and commonly confused) along California's Central Coast are Godwits, Curlews, Willets and Whimbrels. Marbled Godwit (upper left), Whimbrel (upper right), Long-billed Curlew (center front) The distinguishing featu
Read more

Birding in Adverse Weather Conditions: Wind and Rain

Image
Though I often extol the virtues and merits of winter in the Central Valley , especially when it comes to birding, the whole truth is that we experience "bad" weather also, just like anywhere else.  But even when the winter weather rolls in, the birds are still out there!  And sometimes, despite our best planning efforts, a birding day happens to coincide with crummy weather.   In that case, what's a birder to do?  Usually, we go birding anyway!   Birders far more intrepid than I regularly brave the ice and snow of northern winters to see their favorite birds, so perhaps you should look to them for real tips on winter birding!  For those of us in the valleys of California, the worst weather we see - wind and rain - is really comparatively mild.  Birding on an extremely windy day! I don't know of anyone who actually likes birding in the rain.  But I would argue that birding in the wind is just as aggravating as trying to bird in the rain!   Wind can be utterly infuri
Read more

Winter Gulls: The Great I.D. Challenge

Image
Gulls are a fun challenge for birders, from beginners to experts.  A few things make gulls an interesting study: they are large and conspicuous in their open habitats, so they are easy to see, easy to put a scope on, and easy to watch and study for long periods of time.  Furthermore, gulls are almost always identifiable as gulls; none of this confusing warbler/vireo/kinglet nonsense! And yet, gulls are almost impossibly difficult!  (Though perhaps not nearly as difficult as Empidonax flycatchers!) An intimidating scene to many a birder: a mixed flock of gulls.  I see five different species of gull here. Oh, and one American Coot in the background. One of the reasons they are so complicated is most gull species take two or three years to achieve adult plumage, and go through multiple molts in a year.  So, you may be looking at three or four gulls together that look like four completely different species, when they are actually just different ages (individuals in their first, s
Read more

Joshua Tree Woodlands: A Tale of Sloths, Moths and the Trees that Need Them

Image
In 1844, early California explorer John C. Fremont gave a somewhat scathing review of Joshua trees when he wrote, "...their stiff and ungraceful form makes them to the traveler the most repulsive tree in the vegetable kingdom."  Rather unkind, don't you think?  But when Joshua trees were formally described by scientist William Trelease in the 1890's, he noted that Joshua Trees are "the most attractive of all the Yuccas."  I am inclined to agree with this sentiment, and must disagree most heartily with Lieutenant Fremont! I, for one, adore Joshua Trees, with their whimsical shapes and great ecological significance!  If you struggle with plant identification, the iconic Joshua tree, hallmark of the Mojave Desert, is a good place to start.  With densely spiked tufts protruding from the ends of gangly arms stretched towards the heavens, this looks like a plant straight from a Dr. Seuss book.  Native people called these trees “humwichawa,” and used thei
Read more

What's Wrong With This Tree?

Image
If you've spent any time in an oak woodland (and I sincerely hope that you have!!) you may have noticed something odd: strange growths on the branches and leaves of oak trees.  You might wonder if the trees are sick or diseased, or plagued with a dangerous pest. But not to worry; these fascinating growths are a normal part of a healthy oak community.  Spined Turban Gall on Valley Oak, with a bonus gall: the tiny orange sphere to the left of the larger gall might be a gall of the California Jumping Gall Wasp (inconclusive) These growths are in fact galls, and are caused by a variety of cynipid wasps.  Galls form when a wasp lays eggs in a plant's tissue, releasing chemicals which stimulate the plant to use its own tissue to form protective structures around the eggs.  As the insect larvae develops, it feeds on plant tissue from within its cozy gall home.  Galls form on a variety of plants, including alders, poplars, willows and even sagebrush.  But the best known and m
Read more