Wednesday, October 21, 2020

Geology of the National Parks in Pictures - Craters of the Moon

My next post about the Geology of the National Parks Through Pictures is a park we visited back in 2012 that I had wanted to hit up since it was close enough to me in southern Idaho.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website


Craters of the Moon National Monument and Preserve

My standard park sign picture, but this time with the little one.

Here is a lava tube entrance. Craters of the Moon is located within a region of the US known as the Snake River Plain. The Snake River Plain was created as the North American plate slid of over the Yellowstone Hotspot. A hotspot is a volcano that stays in one place while the plates slide over it, like Hawaii. 
Pathway of the Yellowstone Hotspot across Idaho. Image courtesy of the Digital Geology of Idaho

Craters of the Moon falls to the northwest of the Picabo Volcanic Field, which is dated to 10.3 million years ago. This is the time when the Yellowstone hotspot was located at this point and had erupted. However, the volcanic activity that we see at Craters is not directly related to the Yellowstone hotspot. 

At Craters we can see the result of that volcanic activity by the remnants of lava flows, lava tubes, and other volcanic features. Here we can see a pretty good view of the landscape that has many trees and shrubs but is still pretty barren. There are three separate lava fields within the National Park that range in age from 15,000 years to 2,000 years old, all far younger than the 10.3 million year old Picabo eruption. Craters of the Moon is found along a track of land known as the "Great Rift". 

Within the are there are a lot of dead trees hanging about. The Great Rift is an area of crustal thinning associated with the expansion of the Basin and Range area, as well as deflation of the crust following the passage of the hotspot. So, although the volcanic activity is not a direct result of the Yellowstone hotspot, it still played a role. The combined effect of the crustal thinning and the deflation produced areas of increased volcanic activity, with one of the largest areas being Craters of the Moon.

The above shows multiple rift zones within the Snake River Plain. The large grey areas aligning with the Great Rift represent Craters of the Moon. Image courtesy of the NPS

Within the region remains a lot of extinct volcanoes including this cinder cone. A cinder cone is a volcano that is created by the eruption of lava blocks that eventually pile up to create this rather steep sided pile of rock. He we are climbing up the largest of the cinder cones, Inferno Cone.

 Panoramic view from the top of Inferno Cone.

 View from Inferno Cone of a couple of smaller cinder cones.

Another view of the same lava flow, this time a little further up. You can see both types of basaltic lava flows here, pahoehoe and 'a'a. Pahoehoe lava is the smooth lava, that often has a ropey texture, while 'a'a lava is a more blocky, sharp lava. 'a'a' lava was named for the sound people made when walking across it barefoot. Here you can see a nice transition from the pahoehoe to the aa style lava.

Some nice 'a'a, splatter lava.

 View of an 'a'a lava flow showing large chunks of volcanic rocks.

A lava tube is formed when flowing lava starts to solidify when it is contact with the air, eventually forming a crust on the lava flow. The crust continues to build up as the lava continues to flow through the tube, eventually forming this open space within the lava flow. Here I am entering one of the lava tubes.

 Some nice ribbon pahoehoe lava. I really love the fine cracks that run perpendicular to the ribbon folds.

View looking out of one of the smaller lava tubes, Dewdrop Cave.

Within the largest lava tube in the park, Indian Tunnel. Several places along the length of the tube, the ceiling has caved in giving visitors a nice walk even without the need of a headlamp.


No comments:

Post a Comment

Due to the large number of spam comment (i.e. pretty much all of them). I have turned off commenting. If you have any constructive comments you would like to make please direct them at my Twitter handle @Jazinator. I apologize for the inconvenience.

Note: Only a member of this blog may post a comment.