Twenty Three Hours at UKT NP

South from Kings Canyon, then west towards Uluru. From the folded and faulted rocks of the MacDonnell Ranges, we gradually descended to a typical Central Australian landscape – a flat largely plain covered with long linear red sand dunes. This isn’t barren by any means. The dunes seem to be largely stabilized, based on the abundance of trees and shrubs growing on and between them. The road made gentle cuts as we traversed west. Just enough change in relief to keep me awake while driving. The density of traffic increased for the first time. More passenger cars and tour buses. We passed signs that read” We Drive on the Right in Australia”.

Uluru-Kata Tjuta National Park is a high profile tourist destination. Who hasn’t heard of Ayers Rock (Uluru)? Aussies have been braving the trip here since Gosse “discovered” it for Europeans in the 19th century. Aboriginals have of course lived in the area for tens of thousands of years. Anyway, the popularity of the site increased proportional to access. Paved roads appeared in the 1950s, and at some point Yulara was created. This community north of the park is hosts an airport, shopping mall, and all of the nearby accommodation – ranging from campground to five star resort. It’s clearly designed for tourists to fly in, spend a couple days hitting the attractions, and spend a lot of money. There were of course a fair number of travelers like us, who were making a loop from Alice. We also saw almost a dozen vehicles towing boats or carrying surf boards. These were people on long journeys – the nearest water was several hundred kilometers away, the nearest surf at least twice that.

Yulara was surreal. It reminded me of Disney World. It felt insulated from the raw outback we’d been in for the previous days. Everything was nicely laid out and well landscaped. The various accommodations blended into the surroundings. There were lights by all the trails. The campground had lots of grass to sleep on. The generator complex was thoughtfully placed near the campground. So much for a quiet night.

Once swags were rolled out, we headed further south to the Park per se. Uluru came clearly into view. It stunned me, this big blob of grooved red rock. It looked flat at first; my eyes took almost an hour to adjust and see it in relief. But then, there it was – steep sides, weathering stains, lots of large rounded cavities and a gently rounded top. Like Tnorala, I had no problem conceiving that it was a potent Aboriginal spiritual symbol.

We went to the sunset viewing area. This is literally a large parking lot on a prime rise north west of Uluru. It’s the only permitted spot within the park to stop and watch sunset. There’s a separate sunrise spot on the other side. We were an hour early; the lot was already half full. After finding a decent perspective, we waited. The lot filled up with every sort of vehicle and every kind of tourist. I think we were the grubbiest. The people to our left set up a table and had mixed drinks. I smelled either clove cigarettes or pot.

As the sun gradually set; the rock progressively glowed. It was hard to photograph with much color accuracy, but fun to try. It was lovely to watch the contrast on Uluru’s grooves increase, the shadows in its cavities darken. It was hard to both absorb the view and take pictures. I wondered if this view meant anything to the local Aboriginals. Almost dark. We left in a traffic jam of vehicles headed back to Yulara.

Kata Tjuta, or the Olgas, are a series of rounded rock domes similar in scale to Uluru, located about 50 kms to the west. The crowds at Uluru had turned all of us off, so in the morning we headed to Kata Tjuta to hike. Like Uluru, the area has much spiritual significance to the Aboriginals, so much of it is closed to visitors. I’d wanted to come here since reading about Kata Tjuta in my first Lonely Planet Guide to Australia (1985).

No worries. The Valley of the Winds trail looked interesting. It seemed more interesting than Uluru, if nothing If Uluru is a stunning blob of sandstone, then Kata Tjuta is its sensuous companion. Its domes are smaller, and composed of conglomerate. The much coarser grain size of this material gives them a mottled appearance. I tried to control my reflexive urge to identify clast types. I gave up when I reached double digits.

The trail meandered around and between domes. This is the sort of landscape that’s easy for me to get lost in. Not physically lost, but engulfed in looking at what’s around me. Many interesting rocks. What to photograph. Would the light improve? The day started cloudy, but got progressively clearer. Which lens to use (stayed with the mega zoom). Trying to feel the place for itself, not compare it to my other deserts.

We progressed slowly. Louis took initiative and went ahead while Paul and I took pictures. We were passed by tour groups; young guides, young tourists. Why was that German kid carrying a football?

Eventually, it seemed like enough walking. It was time to drive east, begin the run back to Alice. We covered maybe a third of the trail.

Twenty three hours – one sunset, one decent hike. A quick stop at the Aboriginal culture center: too full of tourists to absorb much. A final pause for fuel and a few bananas.

Like the rest of the Central Australia loop, I feel like I’ve largely seen the surface of things. I’d come back to Uluru and Kata Tjuta for sure. It’s possible to walk around the Uluru, that would be interesting. This is probably the best opportunity I’d have to see Aboriginal culture in context. More on this in a future post. Having seen the place once it would be easier to deal with the crowds. Most important would be the time to sit and just look at the rocks. Precious and present observation, so hard to achieve.

I write this in Perth. Paul is gone, off south with his girlfriend et al. Louis is on walkabout iso the Natural History Museum (I hope). We’re packed and ready to head to the Pilbara tomorrow. I’ll write while I’m up there, although the work and remoteness (off the tourist trail, lord be praised) will make posting slower.

Time to escape to Kings Park.

Kings Canyon – Walking the Rim

We drove the Mereenie Loop Road west and then south from Tnorala. This was a first long stretch of dirt track. It was sandy, rocky, and corrugated. I had to focus on both the track ahead, like normal driving, but also on the road immediately in front of me. Loose rocks and other perils are only visible at short distances. It’s also impossible to drive in a straight line on such a track. I had to constantly weave in search of the least bumpy and safest route. Fun, but intense and active driving. Not much traffic.

The Mereenie eventually returned to bitumen. Our next destination was Watarraka National Park, which featured the Kings Canyon locality; the rim walk there was recommended as one of the best walks in the Red Center.

But first, to swag out. The Kings Canyon Resort was full of clean people and felt too antiseptic after the first nights under the stars. We pushed on, hoping to find a track leading off into the bush. We found tracks with locked gates. I spied an ungated track and took it. It quickly dead ended on the margin of a sand dune. I turned the truck and stalled. Whoops. 2WD wouldn’t get us going, so 30 seconds of 4WD got us going. Good for Louis to learn how to lock the hubs.

Presently Kings Creek Station appeared. This may have originally been a working livestock ranch, but now it’s a campground with camel rides, helicopter tours of Kings Canyon, and other organized activities. It was time to camp. We put up with the constant drone of generators, an occasional helicopter and a runaway camel or two for access to running water (showers, ah) and electric light to cook by.

Kings Canyon is a more or less east-west trending gorge cut into a couple distinct formations of flat-lying Mesozoic sandstone. It looked similar to the rock of the MacDonnell Ranges, but is much younger; I think it’s at least partially debris shed from them during the Alice Springs Orogeny. Whatever its origin, the rocks for yet more layers of red strata.

Kings Canyon is abruptly truncated on the west by erosion. The Rim Walk thus began with a steep climb up several hundred stone steps. The ascent felt fine; all my time running and at the gym paid off. The upper sandstone formation is eroded into “beehive domes”. In essence, the sandstone beds originally fractured in a rectilinear pattern. The corners of these blocks have long since been eroded away. The resulting mounds – the beehives – are the result. That said, they’re really cool. Most of the beehives are three or four meters high. Their surfaces are defined by thin beds, which are cut by vertical fractures. The skin of the beehives is thus covered in a checkerboard pattern. The morning light picked out these textures nicely. The trail wandered through the domes for a couple of kilometers. Nice morning light; much to photograph. At one point I looked back on our trail; the tops of the beehives looked like a series of frozen waves.

We weren’t alone on the trail. We played tag up the steps with an older Aussie couple. The husband charmingly helped his wife over the rough parts. I think he’d told her it was an easy walk. More than once, I almost photographed a young couple who stopped and smooched on a regular basis. Paul and I took so many pictures that our progress was slow; we were overtaken by several tour groups: young Aussies, Japanese, maybe Germans. We eventually passed families with small children who were dragging towards the end of the walk. This population was typical for people we had met earlier in the MacDonnell Ranges. Everyone was typically gregarious and cheerful: a favorite Aussie trait.

The trail eventually came near the Kings Canyon rim. At its narrow western end, the beehives recede and the cliff became knife sharp. This was the Kings Canyon featured on postcards and travel posters. Well, it was dramatic, but small. Paul and I could not help but to compare it to similar canyons in Utah: deeper longer, sharper. I kept telling myself that this was Australia, and it was a spectacular landform compared to the rounded hills and flat plains that surround it. I was happy to sit and watch the light change. We eventually descended.

The road continued on towards Uluru.

Things to come

A couple pix of places that will appear soon.


Kata Tjuta

Uluru

Kings Canyon

Tnorala

On a second day of looking at gorges, gaps, and rocks...

The road eventually turned south, just in time for the sun to continue shining on me from the west. I guess I’ll return to North America with the usual asymmetric drivers tan.

A lookout turnoff appeared. At the base of a larger telecommunications mast I had my first look at the Gosse (or Gosse’s) Bluff impact structure. It was formed when something extraterrestrial – the guidebooks say a comet, although there is no positive evidence for this that I am aware of – hit this part of Australia about 143 million years ago. The hypervelocity impact was enough to make a crater that was 20+ kilometers in diameter. That structure has long since been eroded. What I was seeing from the lookout was its roots; the rocks that were deformed by the impact an estimated 2 kilometers below the surface. Today, these remnants form a range of hills more than 5 kilometers wide. From the lookout, it was clear why the early white explorer Giles called these bluffs. They form a series of sharply eroded, overlapping flat-topped hills that rise from Missionary Plain. A distinct contrast from the rolling spinifex hills on which we were standing.

We made a decent camp several hundred meters off an access road. Accessing what I don’t know, maybe better not to. A second night of frost and wondering why the hell swags are still made in Alice Springs. This camp was notable for its wildlife. I saw brumby tracks all throughout our campsite. Louis went walkabout and eventually spotted a pair of wild horses which looked about the right size to have made the tracks. They came to visit throughout the night. Paul suggested the fire either attracted or agitated them. It just might have been how we smelled too.

After the morning gear drying event, on to Gosse Bluff. I’d discovered we could visit this spot using Google Earth. Driving down the bumpy corrugated dirt road, I imagined viewing the truck on the access road from space. A different way of knowing where I was. I’m used to visualizing locations on maps, but placing myself on a satellite image so precisely felt strange. Almost like knowing too much information in advance.

Gosse Bluff is a circular ring of hills comprised of vertically dipping sedimentary strata. In English, this means the beds trend straight up and down. These rocks were flat-lying at the time of the impact. The massive overpressure of the event deformed them downwards, and they then sprang back, freezing vertically. Think of how a stretched rubber band moves; now imagine several kilometers of rock doing the same thing in the space of a few seconds. I sure can’t; but it’s the best scientific explanation for what’s happened.

The bluff is pierced by a stream on its east side; the access road enters here, stopping at a day use area in the center of the structure. Odd; impact features this size often have some kind of a central uplift. Not here; maybe it was eroded.

We parked and hiked around. I wanted to find shatter cones, which are a hand-scale feature formed in rocks by extraterrestrial impacts; they’re diagnostic of such. This was easy. A sandstone layer in the first bed we walked up to was full of them. They were defined by slightly radiating lines – microfractures – which cut across the layering in the sandstone. I’ll stick a picture in here somewhere. We did not see any cone apexes, but this shape was obvious.

We climbed up the side of on of the bluffs. I took the obvious wide angle and telephoto images. Paul shot video. Louis took pictures, climbed around and kept finding more shatter cones. He has a good eye.

Eventually I just sat. I was struck by how uncanny the bluffs looked. We’d seen plenty of tilted sedimentary rocks in the MacDonnell Ranges, folded by mountain building during the Alice Springs Orogeny. They were of course fractured and eroded, but these modifications occurred in a rational context. Tilting, folding, and erosion are comprehensible. Besides being vertical the Gosse Bluff rocks look – smashed. Fracturing is common in rocks, but here pervasive crushing had broken every layer into shards. The strata remained defined, but on close examination look like a splintered and reassembled sheet of glass. Maybe I was preconceiving this, but it was easy to infer that some catastrophic event had formed these features. However, confronted with the evidence, my mind could not comprehend what happened. I’ve read and studied impacts for a long time, but seeing an actual crater, I could not imagine what happened. The forces and time scale are too far out of my experience.

How would this have appeared to the Aboriginals who lived throughout this area? They would have astutely observed the difference in the rocks that I’ve written about. There’s no other structure like Gosse Bluff in Australia. In the local Western Arrente language Gosse Bluff is named Tnorala. Its mythic origin is in fact both cosmic and cataclysmic. According the interpretation of the NT Parks and Wildlife Service, “Tnorala was formed in the creation time, when a group of women danced across the sky in the Milky Way. During this dance, a mother put her baby aside, resting in its wooden baby carrier. The carrier toppled over the edge of the dancing area and crashed to the Earth, where it was transformed into the circular rock walls of Tnorala”.

I didn’t connect with this story when I first read it in California. Here, looking at the far wall of the bluff, it made more sense than trying to force my mind around an actual impact. This place is Tnorala in my mind from now onwards.

Alice and West

Alice Springs was the obvious place to start. It’s the only town of any size in the Red Centre of Australia. At 30,000 or so people, it has all the necessary services: airport, truck rental, and stores (food, field guides, souvenirs). It’s a real town that largely caters to tourism. I thought that it would be a good place to get over jet lag.

Given the distortions of my body clock, my impressions of Alice are hazy. It’s tucked just north of the west-east trending strike ridges of the MacDonnell Ranges. The airport is south of the hills; we arrived in Alice per se through the dramatic piercement of Heavitree Gap, which is just wide enough for the two lane road, the Adelaide-Darwin railway, and the Todd River. The MacDonnells rise a thousand feet or so above the town. The sedimentary cliffs should have been pretty, but jet lag tunnel vision and lack of local orientation kept me focused where I was going and what’s immediately around me.

Reorientation to Australia. Look right, then left when crossing roads. Walk on the left side of the footpaths and sidewalks. Drive on the left; be very aware when entering roundabouts. It was comforting to shop for food and supplies at Woolworths; I’ve been in equivalent stores all over Australia. I know what brands I like. Finally, someplace where I knew where I was.

The influence of tourism on Alice is obvious. The downtown core has a high density of aboriginal art galleries, many of which sell very powerful original works. Paul did his part to support the Australian economy here. The pedestrian mall features a number of tour agencies and internet cafes. There are also the standard curio shops selling the same Australiana souvenirs that I’ve seen in Perth, the Pilbara, Sydney, Hobart, etc. The gradient of young backpackers increases to the west towards the youth hostel. I’ve heard French, German, Japanese, and possibly Russian being spoken.

We picked up a Nissan Patrol 4WD on Monday. It’s a decent vehicle, a little mushy in the suspension and steering, and the shift gates are a tad fussy. A wider wheel base than the Toyota FJ 100s I am used to. The hire company also provided gear; cook kit, table and chair, and swags. We filled the remaining space with food, gear, and water bottles.

Before setting out, we spent a half day at the Alice Springs Desert Park. It’s a sort of combination botanical garden and zoo. It does a superb job of presenting the major ecological zones of Central Australia within a walkable setting. I wish I had been less jet laggy, I would have absorbed more. The biological context is just different enough from the Pilbara that there was much to see and learn. I pretty much failed. Nonetheless, it was rewarding to wander through a series of small aviaries and see a wide variety of birds, to get a feel for the local species of spinifex (softer) and wildflowers (similar). The nocturnal house featured a colony of bilbys; these are sort of a rabbit-like marsupial that’s almost extinct (due to feral cats). The only odd part was a recurrent sense that this was a created landscape. I don’t know when the Park was opened, but the majority of the vegetation zones had to be installed; all the plants thus were about the same size. It lacked the range of young to old plants that occur in a native landscape, and it was not established enough to look “real”.

On Tuesday we headed west from Alice into West MacDonnell Range National Park. Our route followed a major valley between a couple major ridges of resistant sandstone. For some reason the road is called Larapinta Drive. This amused me, I think of a “drive” as having houses on it. Here it really was a drive, a route to new and interesting places. The main NP attractions are the stream valleys which have cut north through the Ranges, cutting narrow and scenic gorges. We stopped at several of these: Simpson Gap, Standley Chasm, Ormiston Gorge. They were each dramatic in different ways, ranging from the narrow notches at Standley to an outright canyon at Ormiston. Each stop was at most a few hours hike. Time to take pictures and learn a field protocol for fussing with all my camera gear. Also reflexive geology; observing the rocks to understand their sedimentological and deformational history. More orientation.

A first night’s bush camp; a chance for Louis to get oriented to how we do things. First, find the right off road spot. Make sure the truck is parked safely. Collect wood for fire, dig fire pit. Choose swag out spots and lay out gear. Assemble table, cook gear, and chairs. Enjoy happy hour while some one cooks.

A clear night, lovely to be back under the stars. Very cold, to be expected in the desert. I woke up to make use of a nearby bush, and discovered that my swag and gear were covered with frost. In the morning we all discovered that swags aren’t the best cold weather gear. While they kept the frost on the outside, their canvas sides also trapped much moisture inside. My sleeping bag verged on wet. The pad under me was damp. We had a leisurely breakfast while the sun dried everything out.

Alice Springs: Three Tubes Later

6/8/09 6:48 am, Alice Springs

My trip began on BART. My sweetheart dropped me off at the Lafayette station after a long, hard week of preparations. I was feeling pretty ready last week, but then a severe allergy attack and an onerous mental health grant at work interfered. I thus arrived on tube number one with my two bags, a brick of a carryon full of electronics, and a vast selection of anti-allergy pills and tissues. Hard to say an affectionate good bye when one is full of snot and dizzy. Hearts were present.

Paul joined me a few stations down the track. We compared our latest gadgets on the hour long ride to SFO. By counting camera lenses I have the quantitative edge. Nice day to leave home, a beautiful early Bay Area evening – I’m always sad and excited as the tube progresses through the same series of stations – Rockridge, West Oakland, City Center, Daly City, San Bruno, and finally SFO, where tube number two awaited.

Into the SFO international terminal, Louis was already waiting for us at Qantas. Check-in had commenced, but I still managed an exit row middle seat. Dinner, boarding at bedtime. I lugged by wad of electronics down the aisle and plopped onto Seat 58B: near the back of the tube.

Late departure, something fussy in the cockpit. Long slow takeoff roll, then over the Pacific. I thought, good, there must be enough jet fuel on board. Eat, sleep, watch movies, stretch, take drugs, drink fluids, talk to row mates. They were both Aussies returning home. Intelligent but necessarily insular views of the US. Typically curious about me and my opinions about Australia. Neither of them had been to the Pilbara: no surprise there. Leg room good.

The tube was an aging 747-400. This turned into a plus as my right hand row mate’s entertainment system failed to function. As compensation, the steward brought her a duty-free bottle of champagne (Charles Krug), and gave all three of us first class toilet kits, express customs passes, and energy drinks before landing.

Sydney at 6:20 am, about on time. Pre-dawn. Express customs was handy, although my rock hammer proved of interest for the first time ever. We stumbled to the domestic terminal, in search of tube number three.

A mocha and a doughnut later, we boarded a 737-800 to Alice Springs. I chose a window seat. I entered the jet lag zone. The adrenalin of landing in Australia and passing customs had faded. I forced myself to stay awake and watch the new and unknown landscapes pass under the plane. Lots and lots of red linear sand dunes, punctuated by dry lakes. Must have been horrible country on foot or horseback for the 19th century explorers, although the aboriginals thrived there for tens of thousands of years. I’m sure the current Murray River Basin drought made the land redder and drier than normal.

My travel karma continued. I had requested vegetarian meals when I made my Qantas booking. When handing out lunch, the flight attendant said, that’s a small sandwich for such a big guy, have another.

Onto the tarmac at Alice Springs just after midday. I am done with long aluminum tubes for a while. Or at least for a week. I’m looking forward to getting the truck and going into the country tomorrow.

Yesterday before dinner, in an effort to stay awake, went to aboriginal art galleries. Paul was game to purchase some new pieces. He’s thorough so I had time to look at many works in detail. Through the jet lag, saw a broader range of painting than I’ve seen in earlier years. The gallery staff was glad to chat, so I learned a couple interesting things. First, the art movement burgeoned here in Central Australia because it was about the last part of the country where Aboriginals were contacted and culturally influenced by whites, that is, they were less screwed over and disacculturated. Some of the first missionaries hooked them up with painting, and the art movement took off. This seems to explain the lack of art in the Pilbara; most of the natives there were disturbed many decades ago (I think). We saw some powerful works by a guy about my age who came out of the bush after meeting his first white man in 1984. Amazing; this was only one year before my first trip to Australia.. Second, contemporary aboriginal art is getting more colorful and abstract, instead of earth-hued and pointillistic. Also less overtly Dreamtime-related. Most of this is change is driven by women; the men seem to stick to traditional methods so far. Not sure why this is so. I’ll see what else I can learn.

Setting the Scene IV: Cast of Characters

This trip has is a party of three. In addition to me, I’m joined by Louis, a geology and trumpet double major from Oberlin, and my buddy Paul.

I’ve already written of my needs and motivations for coming on this trip. Why are Louis and Paul here? I met Louis at Oberlin in March back in Ohio. My colleague Bruce, who’s really a fourth member of the expedition in absentia, thought he had potential to bee a good field assistant. Bruce has probably picked close to a dozen assistants from the pool of Oberlin geology majors. He’s guided by their competence as evidenced by their grades as well as personality. His picks have been pretty good over the years, though we have learned that it’s hard to tell how some one will behave on the far side of the world from home till they are there. Past experiences have ranged from the highs of students who thrived and were real benefits to the project to the lows of occasional depression and chronic flatulence. Louis seems self possessed and intelligent. Bruce described him as being very smart, quiet and serious – “kind of like you when you were at Oberlin”. I am looking forward to finding out what this means.

Paul and I have been travel buddies for most of this decade. This is our fifth long trip past destinations have included the American Southwest, New Zealand, and Australia. We have congruent interests and tolerances. We enjoy each other’s cooking. I think perhaps too we’re a good balance of extrovert (him)/introvert (me) and sybarite/acetic while being equally adventuresome. Paul is only attending the Northern Territory portion of the trip; his girlfriend is meeting him in Perth. From there they’ll go wine tasting in the Margaret River region and snorkeling in the Ningaloo Reef complex; both are gems of Western Australia. While Ningaloo is very cool, I’m not covetous. Besides tending to sink in water, I’ve never had a good snorkeling experience: something to do with the facial hair.

My goal is for us all to enjoy new places and experiences. Intuitively, I believe we are a good match up. I’ll note my accuracy as we progress.

Setting the Scene III: Why Go? - The not geology

Why go to Australia again? Besides the research project, several motivations drive me.

First, the adventure. I relish the challenge and test of travel to new places. I’ve been to Aus many times, but each visit is a little different. The work takes me different areas and carries different responsibilities. Each time the land is different, for example, through climate change (drier) or the proliferation of iron mines. In addition, this trip includes my first steps in the Northern Territory. I greatly look forward to seeing and feeling new country. Alice Springs, the MacDonnell Ranges, Tnorala, Uluru, Kata Tjuta, what are they like?

Second, the Nikon. I started taking photographs in 1980. It’s been a rewarding but spontaneous pursuit. Last year, in search of more personal happiness, I chose to get more serious about the craft On this trip, my kit includes a DSLR, lenses, tripod, filters, and all the cleaning gear needed for fussy electronic cameras. It’s a test. I’ll have time – and the places – to compose and create images that are well beyond snapshots. I feel the pressure to successfully apply the concepts and technology I’ve learned, and the excitement to see what compositions occur.

Third, the change. Time away from my home, usual places, and daily rhythms breaks the grip that normal routine has on my mind and spirit. On long trips, especially when I spend much time outdoors, I balance and connect with the parts of myself that are repressed by the speed and requirements of my daily life. I return more authentic and balanced, often in shock at the compromises I have unconsciously made. There’s always a post-trip window of time when I can make adjustments. At this point much of my life is in flux; I could happily change what I do for work, I’m ready to change where I live, and I’m approaching a more creative life. It might be time to open a dojo, or make some other radical life move.

Finally, Australia. I like the place. I became a desert devotee in the American Southwest. The red, arid landscapes of the Pilbara and the Gascoyne have also become close to my heart. The reasons are complex. The barren rocky landscapes are beautiful. Knowing their geology enhances this. In addition, these are the landscapes of my maturation. I learned to love travel through my trips to Australia during grad school. I grew intellectually through my work, and emotionally through my time in the outback.

Setting the Scene II: Why Go - Geology

All of my trips except for 2006 have been to Western Australia, where I’ve done field work as a grad student and in my part-time career as a geologist. I completed my Ph.D. research on a suite of volcano-produced underwater landslide deposits (fine-grained turbidites and other density flows comprised of hydrovolcanic material for those of you who want to know). Since 1993, my colleague Bruce Simonson and I have worked on a set of meteorite impact deposits.

Let me explain this briefly. The Hamersley Basin strata – the sedimentary rocks – that we work in were deposited on the ocean floor, between about 2.7 and 2.4 billion years ago. Yes, that’s billion: they’re a little more than 50% of the Earth’s age. This was long before multicellular life evolved, although there was plenty of slime such as cyanobacteria around. These rocks have subsequently been uplifted and exposed on land in Western Australia. They are in exceptionally pristine condition. Unlike most rocks of their age, they’ve experienced essentially no mountain building, and remain flat-lying, as they were formed. It’s possible to trace individual layers for tens of kilometers and sedimentary features haven’t been destroyed. Most sedimentary geologists would kill for this kind of availability. The rocks are also largely unaltered by post-depositional chemical processes. Many close to primary textures and minerals are preserved. Finally, the lack of advanced life forms means that the physical structures that formed when the sediments were deposited remain undisturbed. Such features in more recent rocks are commonly erased by burrowing marine organisms – worms and the like. The point of this – the Hamersley Basin is a great place to study sedimentary rocks.

On our first trip we found a distinctive sedimentary layer that we called the Spherule Marker Bed: the SMB. Unlike all the other Hamersley Basin strata we’d seen, it contained lots of sand-sized spherical particles. Within a year, Bruce figured out that these were best interpreted as material that was deposited in the Basin after a very large meteorite impact. When an asteroid a few kilometers or so in diameter hits the Earth, much of the asteroid and the target area it hits are vaporized or converted to molten rock. This material blasts up into the atmosphere, and probably into space around the earth. Somewhere in the process, the vapor condenses into spherical droplets, which together with the molten rock rain back onto the Earth’ surface. The SMB is one of these deposits. In this case the impact debris ended up on what was then the ocean floor. Bruce deserves full credit for sorting out this interpretation, which is pretty firm. The spherules don’t look like normal terrestrial particles. Geochemical work also points to an extraterrestrial impact.

My focus has been on what happened after the impact. The SMB isn’t a simple layer. It shows much evidence of catastrophic reworking by both tsunami and underwater landslides (high and low density turbidites). My best interpretation of what happened is that the impact took place in the ocean. After the layer formed on the seafloor, tsunami generated by the impact arrived, eroded and then redeposited this bed. The tsunami continued on, and struck relatively nearby land areas. Tsunami run-up and backwash triggered or contributed to the subsequent underwater landslides, which again eroded the original layer and deposited a new one – the SMB we see today.

A final exciting part of this work has been discovery of more than one impact deposit. We’ve found at least three more, each of which represents a different impact. They’re both above and below the SMB, separated from it by hundreds of meters of rock. All of them show evidence of extreme reworking like the SMB, which has strengthened my interpretations. Moreover, all of these impact deposits have been found in South Africa, in rocks very similar to the Hamersley Basin. This is important as it lets us correlate time. The impacts occurred essentially instantaneously on a geologic scale, so, they are like time lines that tie the two areas together.

All of these discoveries; the SMB and the other layers, their sedimentary histories, and the intercontinental correlation are important to understanding Earth history. These layers are arguably the best-preserved impact layers of their age. They're in much better shape than most younger layers. The depositional history I’ve worked out is important in understanding what might happen in the future. There are plenty of meteors, asteroids, and comets in the Solar System that might strike the Earth someday. If you want to worry about this, visit www.spaceweather.com.

Setting the Scene I

After counting on my fingers numerous times, I’ve determined that my 14th trip to Aus starts on June 5th. Past trips were in 1985, 1986, 1987, 1989, 1993, 1996, 1997, 2001, 2003, 2004, 2006, and 2007. I’ve written travelogues in the past and posted them to email. I thought a blog might be fun this go round. Have laptop, will write.