SJAA Ephemeris July 2001 | SJAA Home | Contents | Previous | Next


Walking On The Moon

Dave North

I'm drawn to volcanism, perhaps because of so much collateral exposure from reading about the way the Moon formed.

Or maybe it's just that whenever there's a volcanic feature in a National Park, it's the Devil's Legoland or some such stupid name.

Lassen is no exception, but I'll spare the gory details - the main subject is simply called the Cinder Cone, which is a great name for it!

Cinder cones are all over the place on the Moon, so this was a chance to walk on a similar feature without the price of a lunar ticket.

You wanna see the Moon close up and cheap, go to volcano parks!

It's easily reached in a short day from San Jose, but you Hawaii members will have to pick out a local one to inspect instead...

Lassen's cinder cone is a real oddball. For one thing, it's close to symmetrical, which makes it very lunar in nature. But that's rare on earth!

Why? The prevailing wind usually deposits more ash on one rim of the crater than the other, building it up. So most look like a conic section was sliced off-horizontal.

Best guess is there wasn't much wind, so it mostly just built itself up evenly.

Another oddity is the structure of the central crater: it's a double! Apparently the cone erupted, stopped, and rerupted a bit less violently. This is particularly neat to see, and unique in my experience (though probably not all that uncommon).

Before we get too technical, I'll dwell a bit on the magnificence of being atop this structure: it's incredible.

It pokes up above just about everything nearby, and presents Lassen Peak from a particularly good angle. The flows and ash falls around the cinder cone are spectacular, both in their hummocky form (very Moonlike!) and incredible range of colors (very unMoonlike. The colors are oxidized iron for the most part, and there just isn't oxygen on the moon. Consequently, it's one of the more color-starved places in the solar system).

It's windy, as are most peaks that jut above surrounding territory. At times, the air can toss you around a bit.

Getting atop it gives you some idea how steep the sides are: it's a very tough climb. In fact, when you first see the path, you have trouble believing such a steep trail exists in a National Park (and then you remember the climb to the top of Lassen Peak - oh yeah).

The cone can remain so steep for so long because, ironically, it's so porous. Rather than being eroded by rain, the water just soaks right in and down before it can form streams or even runnels. In places, I'd swear the sides ascend at an angle greater than 45 degrees, which hardly seems possible, but my impromptu arm-protractor gave such a result.

I couldn't help but wonder how similar some of the cinder cones on the Moon might be: if they were equally steep, they may well still be, with no erosion at all save for the "grooming" from dust and small particles hitting the moon.

The surface is surprisingly smooth and crunchy, but not powdery.

And dull black as only basalt can be. In that regard, I think it probably gives a fair lunar impression. And that could get oppressive after a while - at least when there is contrast present.

Looking from the bland cinder cone to the bright terrain surrounding it makes the environs seem, if anything, more brightly painted than they otherwise might impress.

I have no idea how long we spent up there, maybe something on the order of an hour. We circumnavigated the cone, then walked down to the second, interior, cone and considered the cairn at the bottom.

The sides are steep! Whenever a larger stone lets go, it rolls further than little pebbles. The largest make it to the bottom, both on the outside of the cone and the inside.

Outside, they are lost in the general rubble, undergrowth and ash. But inside, there is nothing but a pile of stones in the middle of the inner crater! It's a neat effect, and a great example of mass wasting (movement of rocks and soil without an obvious erosional effect. Winds play a small part, and temblors probably play the largest part. In recent eons, most shakers on the Moon were probably caused by impacts, large and small).

So, even here on Earth, it's possible to get a pretty good look at some lunar features.

To - by proxy - walk on the Moon.

Mail to: Dave North
Copyright © 2001 San Jose Astronomical Association
Last updated: July 19, 2007

Previous | Contents | Next