do Lava Tubes Look Like?
at a Lavatube Entrance - painting
by a NASA Artist
of Lavatubes on Earth
These pictures of Subway
Cave in California were taken in the fall of 1999 by Bryce
Walden and Cheryl York of the Oregon L5 Society. All of these pictures
are © 1999 Bryce Walden (email)
Cheryl and I went to Subway Cave and I've processed
the pictures (arrrgh - dust motes on the lens!) and I'm including a
selection with this note. Those of you ... interested in building an
image of a lavatube base may find these particularly interesting. ... I
took some of the pictures from "floor level." The others, taken
standing, would be from a lunar scale height of 17.5 meters high (I'm
roughly 1.75 meters tall). The "floor" pictures, actually about 6" from
the floor, translate to a lunar scale height of 1.5 meters, about
Subway Cave is the largest of several caves, including
some "ice caves," in the Hat Creek Lava Flow just north of Mt. Lassen
National Park. It's a few miles south of the Hat Creek Radio Astronomy
Observatory, involved in the Search for Extraterrestrial Intelligence.
The Hat Creek flow erupted from fissures within five miles of Subway
Cave that opened up 2000 years ago, roughly the same time as the Cave
Basalt flow of Mt. St. Helens where we find Ape Cave (hm-m-m-m).
As you will see in the images, Subway is a "model
cave" with flat, clear floors (mostly) and smooth-finished walls
curving to an arched ceiling. It was dustier than I remembered, which
may be due to its proximity to Mt. Lassen that erupted violently in
1914. Certainly the tan-colored dust exhibited the kind of behavior
we're used to, easily becoming airborne and seeming to get all over my
camera lens. Luckily I discovered this early on and reduced the damage
by blowing the lens off before each photo. The rest of the damage
(circular haloed bright discs - unfocused dust particles -- littering
the image) I "repaired" in Photoshop, doing my best to remain true to
the underlying image. It should be good enough for government work!
The enclosed ... JPEG images are 640 x 480, 72 dpi. If
anyone wants a larger image, say for a larger monitor or for
higher-resolution needed for printing, the original images are 1280 x
960. Ask and
I'll send you a copy. (One image was slightly skewed in the original.
After rotation and cropping it's not exactly 640 x 480.) If you want a
copy to use as a "desktop picture" on your monitor, send the pixel
dimensions and I'll trim to an exact fit, if you wish. Also, I should
be able to create the image in most common formats, please specify. A
Photoshop native image is around 1.3 MB file size.
For those of you who are interested, Cheryl is
preparing a web page collection of photos from our trip to the Mt.
Lassen area, including such colorful places as Boiling Springs Lake,
Devil's Kitchen, and Bumpass Hell. We stayed at Drakesbad, the only
resort within the boundaries of Lassen NP. When she gets it done I'll
post a pointer.
OTHER NOTES OF INTEREST:
One of the enclosed pictures, "Subway06.jpg" (showing
rockfall in a distant entrance), required a little extra processing to
remove a couple of information signs. That was interesting! I wanted to
remove clues to the real scale of the cave or signs tying it to Earth.
The cave pictures were shot using only the built-in
flash of our little Olympus camera. Considering the challenge, the
camera did surprisingly well.
Just for the record, I really don't expect to find
lunar or Martian lavatubes in such good condition. I find value in
these images in giving the "underlying structure" of the lavatube
environment. And, there may be relatively small sections of a few
lavatubes that do approach these conditions.
Lavatubes on the Moon and Mars are expected to be
quite similar in general characteristics, but larger in somewhat
inverse proportion to their lower gravity levels. Sometimes, but not
always. Many flat floors are caused by the flow subsiding somewhat
after the tube formed, and the lava flow "froze" at a lower level than
the initial flow. On Earth, the flat floors are often covered by
surface dust, sometimes several feet thick, imported into the caves by
rain runoff. We can expect variable amounts of rock debris and rubble
from "spallation", having fallen off of the tube sides and ceiling
through seismic disturbance of weaker areas. The sixth picture in the
series gives the idea.
Ten meter cross-sections are common with lavatubes on
Earth. Scale that up considerably for the Moon where tubes should range
hundreds of meters across. On Mars, they will be somewhere in between
in size, still quite appreciable.
In both locations, lavatubes are expected to be of
significant value as thermally insulated, radiation free, dust free
"lee" environments for outposts, warehousing, industrial parks,
archiving, agriculture, etc.
On the Moon, the domain of lavatubes are the maria
lava-flow sheets. On Mars, we will find them throughout the slopes of
the major shield volcanoes: Olympus, Ascraeus, Pavonis, Arsia, etc.
We tend to look at both the Moon and Mars as barren
rock piles. Well, "behind door number one" is a big surprise - both the
Moon and Mars have hidden sheltered valleys, comparative Shangrilas.
And you have all heard the dictum that there are three things vitally
important in real estate: location, location, location.
Lavatubes are the "locational lever" by which we can
move the Moon and Mars from the realm of alien hostile worlds into the
realm of human space.
Pictures from Bryce Walden
Lavatubes - Articles Online from Moon
Online at Space.com
Papers by R.D. "Gus"
L5's Lavatube Links & Photos
of Craters of the Moon National Monument, Idaho
Back to LRS/MMM Papers