Tuesday, May 8, 2012

April 30, 2012. Craters Of The Moon.

 Here's where the Hawthornes are:
Welcome to Craters of the Moon
National Monument and Preserve
 at the base of the Pioneer Mountains.

 The Hawthornes are checking out the Visitor Center first.

 Like artillery from a cannon, hot blobs of lava are shot from volcanoes during eruptions.  This 'breadcrust' bomb is named for its crusty, fractured surface.  Ribbon bombs, spindle bombs, and 'cow patties' are also found at Craters of the Moon.

 Limber pines withstand the stressful high desert climate by bending to the force of unrelenting winds.  The twisted trunk of this tree persevered hundreds of years by yielding to the wind rather than fighting it.

 Many visitors are curious about these cement bases lining the loop road, which in fact hold snow poles.  Difficult to imagine during the searing summer heat, Craters of the Moon receives three to five feet of snow in the winter.  Snow poles mark ski and snowshoe routes - as well as the road location for snow removal equipment in the spring.

 Miles and miles of lava ... but where is the volcano?
Instead of erupting from one enormous volcano,
the lava oozed up from deep cracks that start near here
and stretch 52 miles to the southeast.

This satellite view shows the lava fields
 of Craters of the Moon
and the trend of the parallel fissures known collectively
as the Great Rift.

 In the early stages of a basaltic eruption,
lava is highly charged with gas.
Frothy lava shoots into the air,
cools rapidly, and falls as cinders,
encircling the vent.  
As cinders build up, a cone is formed.
The high volume of dissolved gases in cinders
causes them to spray explosively into the air.

Pahoehoe (pa-hoy-hoy), a relatively smooth lava,
takes its name from the Hawaiian word for "ropy."
Pahoehoe lava flows are highly fluid,
flowing easily.
As the surface of the flow cools and forms a crust,
the hot lava flowing underneath pulls the top layer
into ropes or coils.
The crust eventually becomes a rigid roof,
forming a lava tube.
Pahoehoe's relatively low silica content 
and high temperature cause it to pour over the landscape.

A'a (Ah-ah) is Hawaiian for "hard on the feet:"
a'a lava flows have rough, jagged surfaces.
It is more viscous than pahoehoe,
and therefore flows more slowly,
moving as a mass of broken rubble.
A'a flows are often impassable to those traveling on foot,
quickly chewing up hiking boots.
A'a 's relatively high silica content and lower temperature
cause it to form jagged clingers of lava that 
slowly tumble forward over the landscape.

 Block Lava
A variety of a'a, block lava is thicker and denser,
often having a smooth, glossy surface.
It creeps at a slow speed,
leaving irregular blocks of lava
up to three feet wide in its wake. 

Magma formed from melting of the earth's crust is 
rich in silica and erupts violently,
producing a rock called rhyolite.
Its light color is due in part
to its low iron content.
Rhyolite is the rock found at Yellowstone,
and beneath the basalt at Craters of the Moon.

 Breadcrust Bomb
Large pieces of basalt lava thrown
into the air during an eruption 
are classified as "bombs."
Breadcrust bombs occur when the exterior
of a molten bomb cools before the hot interior
finishes expanding.
The surface fractures, producing the effect of a
freshly baked loaf of bread.

 Blue Dragon Lava
Blue Dragon lava is the name given to pahoehoe
having a purplish-blue tint and a glassy surface.
A unique chemical composition 
and hundreds of tiny crystals
cause the lava to appear blue when light strikes it.

 Tree Molds
When molten lava advances into a forest,
trees are engulfed in a river of molten rock.
The trees burn,
releasing stored water as steam.
The steam cools the lava enough to leave an impression
of the burning wood.

 Outside the Visitor Center 
is a botanical display of indigenous plants
showing how they survive in what can be a brutal environment.

" To understand the West,
you have to get over the color green;
you have to quit associating beauty with gardens and lawns."

In 1980, park researchers tagged a two-year old doe
with yellow streamers on both her ears.
Over the next nine years, 
"Double Yellow was sighted
over a hundred times,
and gave birth to at least a dozen fawns.
In 1989, Double Yellow was killed by a car
as she crossed the highway here.
Her probable goal was the grass
of the visitor center lawn.

Lawns were drinking up 80% 
of the water used in this park.
Planting lawns encourages non-native plants to grow.
Lawns need toxic products to stay green.
Lawns lure deer across the highway.
Replacing lawns with native species saves water,
and protects the plants and animals of the park.

 The lava landscape at Craters of the Moon is a desert environment.  Porous rock, drying winds, air temperatures approaching 100 degrees, and ground temperatures that soar to over 150 degrees - all make the water supply scarce in this volcanic terrain.  Here, the plants adapt to their hot, dry world, or they die.

Great Basin wildrye is a "bunchgrass," a desert grass known for growing in isolated tufts.  The space between tufts reduces competition between plants by assuring each tuft of grass its own territory from which to draw water.

Whenever the water supply is plentiful, prickly pear cactus collects moisture in the spongy tissue of its enlarged stems, called pads.  The cactus can then draw on this stored supply of water when the weather turns dry.

Tansy bush secretes a sticky oil which coats the fern-like leaves of this shrub.  The oil traps water within the leaves, thus reducing water loss caused by the desert heat and wind.

Bitterbrush sheds its leaves during dry periods, and grows a new set when water is available again.  The shedding of its leaves allows the bitterbrush to greatly reduce evaporation during periods of severe drought.

Hundreds of small, light-colored hairs cover the dwarf buckwheat, reflecting sunlight that might otherwise cause the plant to overheat.  The hairs also protect the plant's leaves and stems from the drying wind.

Big sagebrush puts out a shallow mat of roots to absorb rainfall rapidly.  A second, deeper set of roots extracts water that soaks into the soil as the winter snowpack melts.  Finally, a taproot extends downward six feet or more to drink in long-lasting ground water.

Rubber rabbitbrush has small, elongated leaves.  The size and shape of the leaves decrease the amount of surface area of the plant that is exposed to the drying effects of the sun and the wind.

This is Craters of the Moon -
an 1100-square mile area 
which contains more basaltic volcanic features
than any other area of its size in the continental United States.
Lava rivers once flooded the surrounding countryside,
leaving vast lava fields covered by cinder cones with
large central vents that were thought by early observers
to resemble craters on the moon.
Volcanic activity dates back about 15,000 years,
with the last eruptions occurring about 2000 years ago.

This most recent eruption was
 likely witnessed by the Shoshone people.

The Shoshone lived throughout southern Idaho
in small groups, moving each season in search of food.
Bands of Shoshone traveled through the lava fields
of Craters of the Moon.
The area offered little water and scarce game,
but the Indians may have sought tachylyte,
a dense form of basalt used for arrow points and stone tools.

Shoshone legend speaks of 
 of a serpent on a mountain who,
angered by lightening, coiled around and squeezed the mountain until
liquid rock flowed, fire shot from cracks, and the mountain exploded. 
"... Long ago, a huge serpent left its bed where the Snake River is now, and coiled itself around a large mountain to sun itself.  After several days, thunder and lightning passed over and aroused the serpent's wrath.  Angered, it began to tighten its coils around the mountain.  Soon the rocks began to crumble.  The pressure became so great that the stones began to melt.  Fire came from the cracks and liquid rock flowed down the mountain.  At last the fire burned itself out; the stones cooled off; the liquid rock became solid..."

Geologists predict Craters of the Moon will erupt
again within the next 1000 years.
A sudden increase in local earthquake activity
could mean that magma is once again
forcing its way up the Great Rift.

A seven-mile loop drive,
open mid-April to early November,
takes about 30 minutes to complete,
unless you're like Rosie
and order Mr. Hawthorne to stop at every volcanic feature.

At first glance, this places appears to be a desolate jumble of rocks, well-named for its resemblance to the moon's surface.  But look closer and you will see patterns in the flows of lava and piles of cinders - patterns that reveal a story of recent and recurring change.

Between volcanic episodes, plants populate the new landscape and wildlife finds ingenious ways to survive and even thrive in this extreme environment.

This volcanic field is a geologic wonder cast in a wild and remote landscape.  Its central focus is the Great Rift, a 62-mile long crack in the earth's crust and the source of a remarkably preserved volcanic landscape with an array of features - craters, cinder cones, lava tubes, deep cracks, and vast lava fields.
All combine to create a strangely beautiful volcanic sea on central Idaho's Snake River Plain.

The volcanic area now lies dormant, but during its eight eruptive periods, sixty lava flows formed which traveled as far as 45 miles from their vents.  Some of the lava flowed around areas of higher ground, forming isolated islands of vegetation called "kipukas."  Today, these kipukas provide a window on the vegetation communities of the past.  They contain some of the last pristine vegetation in the Snake River Plain, including 700-year old juniper trees and relic stands of sagebrush and native bunchgrass.

 Between 1840 and 1870,
over 240,000 emigrants traveled through Idaho
on the Oregon Trail.
The part of the trail that runs through the Monument -
Goodale's Cutoff -
followed an existing Indian trail.
It skirted the edge of the lava
at the base of nearby foothills.
Enjoy the ride through Craters of the Moon.

Over 300 species of plants live in this seemingly desolate terrain.

Lava cascades.





1 comment:

zzzadig said...

OK, I'm jealous again....