Six days in the crater, day three

Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6

This post is part of a slowly unfolding saga of my experience at the Meteor Crater Field Camp that was held from October 17-23, 2010. The field camp was run under the NASA Lunar Science Institute and headed by Dr. David Kring of the Lunar and Planetary Institute.
This post also doubles as my entry into Accretionary Wedge #49: Out of This World, which focuses on extraterrestrial geology and terrestrial analogues. Thanks to Dana at En Tequila Es Verdad for hosting this month’s Wedge!

Tuesday, October 19, 2010.

From above, our deluge of sun hats would appear to run into and froth against the tourist rope corral for a moment before spilling over and around into the area of No Trespassing. Rapidly arriving at a flattened part of the rim, we diffuse and come to rest, idly shifting for something in our backpacks and maybe a better view into the crater. David starts speaking of the plans for the day, and it takes us a few moments to realize we’re looking in the wrong direction. We turn around and he points at a small hill near the side of an access road. Pondering aloud, he wonders What do you suppose that boulder is doing on top of that hill?

Hint: It’s not a geocache.

The plains surrounding Meteor Crater are afflicted with an excess of flatness. Aside from the crater itself, the only relief is from scattered blocks, mounds and low rises of Coconino Sandstone and Kaibab Dolostone. They are blemishes on the otherwise flat patchwork terrain surrounding the crater. Like the boulder on the hill, many large coherent blocks of ejecta excavated during impact were thrown out of the crater and now rest upwards of 300 feet above where they ought to. Three days in, we were no longer tourists; It was time for science. We started work to answer a few relatively simple questions: Where in the crater did those blocks originate? How big are they? What would it take to launch them tens and hundreds of meters to their current position?

To answer those questions, the group split in two. One team examined the ejecta blocks, recording their dimensions and lithology. The other team measured the distance from crater to ejecta, using a physical measuring tape and recording map position and GPS coordinates to cross-check calculations. It was a rather straightforward assignment that also got us thinking in terms of cratering processes. The furthest blocks we studied were a solid five minute walk from the crater. It is easy to lose sight of something that is no longer present, but after the initial impact we would have been scrambling over several additional meters of ejecta the whole trip.

The measuring group stands on the rim of Meteor Crater as the tape is prepared for the trek to ejecta block E-3. Some members of the lithology group are visible on the white block of Kaibab (limestone) in the distance.

Team Tape and Team Lithology knocked out six profiles over the course of the day, including an assessment of the famous three-story-tall House Rock (a.k.a. Monument Rock). Six blocks is a small sample set to be sure, but one that lays the groundwork for a more thorough and complete ejecta study to be conducted over a number of Meteor Crater Field Camps. With a few simplifying assumptions – radial path, ballistic trajectory, 45 degree angle of ejection^† – our results indicated flight times for these boulders of three to fifteen seconds at ~60-360 km/hr [~15-100 m/s]. These velocities get well above hurricane force winds (though they pale in comparison to the ~12 km/s impact velocity). And we’re not talking about shingles and trees flying around – these are multi-ton boulders getting hucked out in all directions. Given enough force, ejecta can go anywhere. House Rocks might not get very far, but there are loads of examples of ejecta traveling hundreds of kilometers, into the atmosphere, or even off-planet. We only have fragments of Mars as a result of a few impacts into the martian surface sending material into space and eventually to Earth. Simon Wellings (@metageologist) wrote a bit more about the evidence of impacts in his contribution to the Wedge, What came from outer space.

The Apollo Era really brought to light the importance of impact processes on the evolution of planetary surfaces. Apollo missions also proved a challenge to geologists. No lunar material was collected in-situ, which means the provenance of many samples is uncertain. The provenance of regolith (soil) and impact breccia fragments is still the subject of intense debate. Many of these fragments likely have origins in basin forming events (e.g., the Sea of Tranquility). Boulders like those surrounding Camelot Crater in the above photo, are a bit easier to reconcile with their source. Mapping the distribution of ejecta lithology around terrestrial and lunar craters is the ground-truth to theoretical distribution models. Gravity and atmospheric conditions may differ between the Earth and Moon, but the results of an impact are similar across the solar system.

Top: Boulder field at Camelot Crater from the Apollo 17 mission. Panorama compiled by Warren Harold of NASA/JSC. Bottom: Looking outward from the rim of Meteor Crater. Both images are in color.

^†Learn more about impact cratering processes with the Lunar & Planetary Institute Impact Cratering Lab

Cosmic Stopover?

Mumford and Sons take the stage in Dixon after a long day full of great music http://t.co/O2BWGoWR

—
Jam Productions (@jamusa) August 19, 2012

After a long day full of fantastic and varied music, Mumford & Sons took the stage in Dixon, Illinois as part of their Gentlemen of the Road Stopover Tour. After warming up with a slow-paced lover’s lament, we jumped right in to Little Lion Man and just kept going. Hits and soon-to-be-new-releases were mixed in fair abundance, and will definitely go down as one of my favorite concerts. There was even some icing on the cake:

Mumford & Sons brought out Jerry Douglas (who would put on a separate show in Dixon later that evening) to play their cover of Simon & Garfunkel’s The Boxer. The stage lights began to dim as they played the opening licks. Between then and the opening lines, almost directly above the stage behind a thin veil of smoke and clouds, a fireball blazed from stage left to stage right. I heard a few “Wow!”s and “Did you see that?!”s, but crowd memory is short and the forces of nature on stage took rein. But I will remember, and I hope those people will, too.

I’m sorry to say I didn’t have a watch/phone to check the time – and didn’t think to ask those nearby – but as I said it started when The Boxer started. It appeared to travel N/NW, and was probably 45-60 degrees above the horizon, lasting less than 2 seconds. Because of the smoke and cloud cover, there is a small possibility that this was a firework. However, I did not see a smoke trail, no other fireworks were shot off, and it did seem to be behind actual clouds and not only smoke. Therefore I hope others will report their sightings, here or elsewhere so we can know for sure!

Have you seen this migmatite?

33 years ago on her first day of work at a hospital, my friend’s mother inherited, in her words, an “antique doorstop and/or paperweight …we think it is petrified wood”. It is fist-sized, shiny, and much heavier than it appears. It is stumpy and rhombohedral-ish, with many semi-parallel lines along the sides and curving bands along one face. It kind of looks like petrified wood…but it is not. Far from it.

The mystery migmatite. Dime for scale. Click for full resolution.

Petrified wood results from rapid burial and slow hydrous alteration into silicified casts (permineralization). Lying underground in a wet, mineral-rich environment, picking up hues of red and yellow and gray. Calmly, coolly, entirely without incident. A history about as far removed as possible from the sample that arrived in the mail over the weekend. Migmatites (from the Latin migma for mixture) are the product of intense heat and pressure that result both high-grade metamorphism and partial melting. Check out the Georneys post M is for Migmatite for fantastic coverage of all things migmatite.

“far side” of the migmatite from previous photo. Was there a vug/gap here that allowed free crystallization?

What’s missing from this story is the provenance (origin) of this fantastic rock. Not all migmatites look the same – some lack the leucosomes (light bands) seen here, and they are not all black-and-white – and my hope is that this sample is from the Pacific Northwest… maybe someone out there knows where. For the past three decades it was hanging out east of the Cascades in Central Washington, which is a good place to start. The crustal accumulation and volcanic history of the Pacific Northwest is a prime migmatite-forming environment. I’ve found references to the Okanogan dome/highlands and the Skagit migmatite as starting points, but detailed online photographic records are somewhat lacking. Now I reach out to the ether: Have you seen this migmatite?

Findings from the USGS Store $1 Sale

The USGS Store $1 Spring Mega Sale ends Monday, June 4th, 2012. I pored through their archives for a couple of days and ended up with 40 items in my basket. Then, of course, after purchasing those i found ‘just one more map’ that I had to have. Total cost: $49 dollars (includes $5 handling charge and two duplicate maps).

Instead of merely posting a picture of my flood of maps after they arrive, it would be more beneficial for y’all if I put my shopping list on display while the sale is still ongoing. Hopefully something will spark your interest or remind you of a map you’d like to have! Product codes are shown with links to items in the store in case my link-fu is poor (If a link fails at first, usually a second try does the trick).

Tolovana Beach sand

Quartz (white) and plagioclase (yellowish) dominate this sand collected from the edge of a tide-pool on Tolovana Beach near Arch Cape, Oregon. The regional geology is dominated by basalt overlying marine sediments.

Feathery Basalt

~1mm wide cross-polarized image of a portion of the groundmass in Apollo 17 high-Ti basalt 71157 (thin section ,8). The "feathery" texture results from the intergrowth of pyroxene (brown), plagioclase (white/gray/black), ilmenite (black), and some glass (black). The other major phase is olivine, which is present on the image borders and forms the plus-shaped cluster at right middle. There are several early literature (pre-1980s) references to feathery intergrowths, but the associated images have degraded in quality (many articles appear to be scans of photocopies).

AW#45: Geological Pilgrimage

The 45th Accretionary Wedge is hosted by the life as a geologist blog, which asks us to share “the sacred geological place that you must visit at least once in your lifetime…a single place, which is ‘geologically’ unique, relatively remote, and requires some difficulty to get to”. Now, pardon me while I take some liberties with the English language to write about the Moon.

That’s right, the Moon. Geologically Unique? Check. Remote? Check. Difficult to get to? Indeed. So much so that a mere eighteen have made the journey to lunar orbit, and only twelve of those have made the descent to the surface. It remains amazing crazy insane to see images and video of the Apollo missions. Human beings! On the Moon! Walking, driving, discovering, singing, and golfing on the Moon! Which brings me to the “once in your lifetime” part of this pilgrimage. The last footsteps on the Moon were made 40 years ago (this December). Back when Nixon was president. Back when there were almost half as many humans on the planet as there are today. Back before I was born. Taking the liberty to use the royal “you” in the call for posts, I would say that yes, the Moon is a place you/I/we must visit at least once in a lifetime.

Every mission was just a few small steps (or drives), but the science grew by leaps and bounds. The final mission, Apollo 17, had the longest surface stay, the first geologist, and the most returned samples, including the highest-Ti basalts in the solar system. Nowadays we’re making progress by taking a step back, with satellites characterizing the Moon from orbit (surface, gravimetrics, ionosphere, etc). Still awesome, but we need a human presence up there to continue exploring and inspiring.

Is the Moon not specific enough? Perhaps…OK, let’s focus on the Aristarchus Plateau. Why? Because it’s there.

The Moon. Aristarchus Crater is an easy-to-spot lunar feature, made even easier by a giant arrow. (Photo by me; 250mm, f/5.6 @ 1/2500s, ISO400; Dec 1, 2009)

Above, Aristarchus Crater is a beacon of light in the low-albedo mare of Oceanus Procellarum. Viewed in another ‘light’, the below RGB image highlights the diversity of features accessible in the region.

Clementine RGB false-color ratio of Aristarchus Plateau, including Aristarchus Crater (bright blue-green, 40km diameter). Image is ~500x500km. Colors are based on UVVIS reflectance spectra ratios (in nanometers) where Red = 750/415; Green = 750/950; Blue = 415/750. See Pieters et al. (1994) for more details on spectra.

False-color ratios are used to demonstrate soil and mineralogical differences, and there are subtle variations that I’m not familiar with to explain concisely. At any rate, the Aristarchus Plateau contains a variety of colors features that we geologists should get a chance to see in our lifetime. To name a few: Pyroclastic deposits, sinuous rilles (collapsed lava tubes?), exposures of cryptomare, highlands, unique volcanism, and possibly the youngest surface basalts¹. For more information on the A.P., start with one of the many LROC featured images of the Aristarchus Plateau.

Resources:

LPI Clementine Mapping Project: Source for the RGB false-color ratio image. Request your own map of Clementine satellite spectra! Make a custom spectra map, or request standard RGB false-color ratios, FeO, TiO₂, or topography maps.

¹Hiesinger, H., et al. (2003) Ages and stratigraphy of mare basalts in Oceanus Procellarum, Mare Nubium, Mare Cognitum, and Mare Insularum. Journal of Geophysical Research 108, E7, 5065, 27pp.

Four years of research poster design

Science conferences are ubiquitous components in research. What are you working on? What are you interested in? What do you want to tell us? Maybe you are allowed to read slides at us for twelve minutes (plus three for questions). Maybe you’ll bring twenty seven eight-by-ten color glossy pictures with circles and arrows and a paragraph on the back of each one explaining what each one is. More likely, however, you’ll have a dozen square feet of real estate on a tack-board. That is enough room for thirteen or so eight-by-ten color glossy photos with circles and arrows and a paragraph on the back of each one explaining what each one is, but the more commonly employed medium is that of the research poster.

The form and function of presentations and posters have their respective merits and drawbacks, and you can find ruminations extolling both of these somewhere else. I am a no preference kind of guy. To wit, I have one of each to present at this year’s Lunar and Planetary Science Conference (LPSC) in March. The LPSC is the main conference our entire research group attends every year. I have had at least one poster at each of the previous three LPSCs, plus two posters at other conferences. With three years under my belt, it should be easy to make a poster, right? Heck, you might say, after three years you should have a Masters of Poster Science! Well…no, it is not that simple.

substance without style is truth without beauty

Communicating science is hard, and only more difficult if conveyed boringly. Whenever it’s time to start making a new poster, my search history fills up with terms like “poster design”, “award science poster”, and “awesome research poster” (see here and here to start). The essence of a research story doesn’t change; My substance is the scientific method. But substance without style is truth without beauty. And with 700 other posters to choose from, would you stop to check this out?:

2009: Fear my wall of text! Size: 42″x34″; Title: Times New Roman 72pt; Body: Times New Roman 30pt

Nope. The color scheme is all right, but there is no hierarchy. What is important here? Graphs are all about the same size, there is no central point of focus, and look at all that text! This was made after 6 months of grad school, so I vowed to focus more on results the next time around, resulting in…

Six days in the crater, day two

Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6

This post is part of a slowly unfolding saga of my experience at the Meteor Crater Field Camp that was held from October 17-23, 2010. The field camp was run under the NASA Lunar Science Institute and headed by Dr. David Kring of the Lunar and Planetary Institute.

Everyone is surprisingly awake at 7AM, considering the hard sun yesterday. Maybe it’s the brisk 50°F October air, or perhaps everyone had a long sleep (one pro of a dry campsite). My hunch, however, is on the catered breakfast of fruit, eggs, coffee, juice, oatmeal, and scones that awaits us. A local Flagstaff catering company will be bringing us breakfast and dinner each day, and no one wants to miss out after our first taste yesterday. Even without the extra incentive, the 21 other field camp attendees are highly motivated, intelligent and capable researchers from around the world. And then there’s me, just writing accidental haiku in my field notes…

base of mining slope;
two tear faults up wall expose
best Coconino.

The Coconino is an eolian quartz sandstone; white, fine-grained, occasionally massive but often with cross-beds. If you’ve never heard of it, perhaps you’ve seen the Coconino cliffs of the Grand Canyon or Zion National Park. At Meteor Crater, the Coconino is the lowest unit excavated by impact, extending from 90-300 meters below the surface. The crater center is buried under ~100 meters of lake sediment, and a mine shaft is the only portal to the original crater floor. Remnant mine talus piles on the crater floor hint at the intense shock buried 100 meters below, where some sandstone was altered to vesiculated glass; It floats! The major occurrences of Coconino ejecta still present around the rim are generally not shocked to glass, but are no less interesting. The Coconino in the photo below is ‘fuzzy’ because it has been pulverized to rock flour, though relict bedding is preserved.

Overturned Coconino SS ‘rock flour’ with relict cross-bedding in northwest wall of Meteor Crater. This coherent ejecta block was originally 90+ meters beneath the surface and now rests ~15 m above the surrounding terrain.

Over on the south side of the crater, heterogeneous shock distribution resulted in relatively unshocked Coconino in contact with the rock flour variety. A useful reminder on the importance of context!

Accretionary Wedge #42: Countertop Geology of two marbles

The Accretionary Wedge is a semi-regular collection of geoblog posts that follow a common theme. Ian Saginor is hosting AW #42 at his volcanoclast blog with the theme of Countertop Geology. For my first ever Wedge, Ian has tasked everyone to:

• Find great countertops or decorative/building stone, as long as it’s been “separated by humans from it’s source”;
• Post some pretty pictures;
• …And maybe hazard an interpretation or two.

Good thing Ian expanded this topic to include decorative and building stone, because it opened up the opportunity to show off two awesome pieces from around the Notre Dame campus. First up is the Kugel Fountain in one of our student centers, the Coleman-Morse building.  The Marble, as some call it, “contains a 30-inch solid granite sphere which weighs 1,300 pounds and floats on 7 lbs. of water pressure” (via the ND website).

Notre Dame's Kugel Fountain. The granite sphere constantly rotates - 'clockwise' during this 1-second exposure - due to minor differences in supporting water pressure.

Take a closer look…

Unlike most granites, you have to hold this one steady to get a decent photo! Large ovoid alkali feldspars (pink) enclose opaques (dark minerals, mostly hornblende), and in some cases plagioclase feldspar (gray) form rims on alkali feldspars. Click any photo to enlarge.