Snow features on frozen lakes

This winter, I’ve started to study snow bedforms. When snow falls, it settles into soft blankets – unless it gets caught by a strong wind. In Colorado, some of our strongest winter winds appear in the Front Range, where cold air falls over the Continental Divide towards the plains. When the wind picks up snow, it forms fantastic, ordered bedforms, like pointed sastrugi:

Sastrugi point towards the wind

and dune-like crescents:, both big:

Snow crescent angled into the wind

and little:

A small snow crescent on a frozen lake

I took these photos with CU-Boulder undergraduate Clea Bertholet for scale.

In the coming weeks, I plan to start taking measurements and (eventually) build a model of snow bedform development in different wind and snow conditions. For now, we’re scouting snow conditions around Colorado.

Glacial sparkles in Yosemite

I open my eyes, slowly. The sun has begun to slide over my hammock and into the hood of my sleeping bag. I push the fabric away. The sky is already a pastel blue, but the pine trees below it are lit by dabs of early morning gold. The soft roar of a gas burner off to my left means that Prof. Grove has just started the first pot of coffee. My toes are warm in their down covers. I don’t swing them into their boots until the last brush of gold threatens to fall from the trees, and I can snap a photo of the now-bright Yosemite sky.

It must be a sin to be this happy on a Monday.

Down the long mountain-slopes the sunbeams pour, gilding the awakening pines, cheering every needle, filling every living thing with joy. – John Muir, My First Summer in the Sierra

I have read Muir’s books often, always smiling with wonder at the love and grace with which he describes the mountains he walks through. His words seem especially apt now, for without his beautiful Sierra morning I would likely never have had one of my own. Muir’s writing and activism drove the preservation movement which led to the creation of Yosemite National Park. Today, this exceptional landscape – once a pasture for sheep or, as he once called them, “hoofed locusts” – is filled with family campgrounds, ambitious climbers, and (starting just a mile or so from the roads) a seemingly endless alpine wilderness.

I came to Yosemite as part of an MIT geology field trip – a bittersweet experience, as I have just started my Ph.D. at CU-Boulder and this was to be my last week with the MIT department. The fifteen of us – undergrads, grad students, an outgoing postdoc and Associate Dept. Head Tim Grove – had nine days to look at the landscape and geology of Eastern and Northern California. The undergrads have described many of our educational adventures in ‘Getting High in the West’.

Granodiorite in Yosemite

Yosemite was built from granite, and is being scraped away by glaciers. Both features make it bright and beautiful.

The raw material, granite, forms when magma cools underground, where heat escapes only gradually to the surface, and its crystals have millions of warm years to grow and interlock. Silicon, oxygen, aluminum, sodium, calcium and titanium are arranged. Clear quartz and white feldspar grow alongside black hornblende, shiny biotite and sphene. The final rock varies slightly with the ratio of elements within it – most of Yosemite Valley is actually made of diorite, granite’s darker and less silica-rich cousin.†

The diorites here are unfractured and exceptionally strong. Yosemite Valley is famous for its cliffs. Half Dome and El Capitan both boast thousands of vertical feet of sheer rock, making them pilgrimage sites for climbers around the world. No photograph can adequately capture the scale of these monoliths (but National Geographic’s photo gallery is a great attempt).

Most rocks would crumble from the strain. Yosemite’s diorite stands tall, except for the top edges of its rocky domes, where the stress of curved slopes and surface temperature changes cause it to fracture and fall off in layers like the skin of an onion. A cliff, however, is only half rock. The other half is empty space. To make a mountain, you must take a valley away.

Glacial polish over Tenaya Lake, Yosemite

The high Sierra has a mirror finish. The ripples on Tenaya Lake shine in the August sun, and so do the sides of the mountain above.

We walked up on the slopes above the lake. At Prof. Grove’s urging, I trained my eyes on the black slivers of hornblende under my toes to look for changes in the rock’s composition. I didn’t see the rest of the valley’s story until I slipped on it.

Granite, in most places I’ve wandered on it, easily holds up my hiking boots. Here, my feet spin like I’m in dancing shoes. Glacial polish – the reason the rocks shine on the hills – is best found by the fingers and the feet. It’s not a climber’s friend. It’s smooth, like a granite counter-top sanded flat right there on the mountain. It feels a little like rubbing your fingers on coarse paper. Once you’ve felt glacial polish you find it everywhere.

Glacial polish above Tenaya Lake, Yosemite


Look at the rock slab under our feet in the bottom-right of the photo above. It’s patchy. The dark patches are rough places, mottled by shadows and by lichen growing in the cracks. In the light, polished patches, there’s hardly a crack. Water doesn’t stay on their surfaces, and plants can’t grip them. They’ve stayed smooth and fresh for over ten thousand years, since the last time that glaciers descended from the High Sierra into these valleys, where their icy sides scraped and strained against the sides, excavating loose and fractured rocks and rubbing the walls smooth.

Glaciers’ traces are visible everywhere in the Sierras. Many scientists have painstakingly cataloged them: glacial polish; deep U-shaped valleys; erratic boulders and moraines (the last two are are carried miles by the ice and dropped on seemingly random plains and hilltops). The first of these was John Muir (c1865), who spent years walking the mountains and demonstrating that Yosemite Valley was once covered in ice.

Glacial striations in Tuolumne meadows

Today, we know that the Sierras have been glaciated, revealed, and re-glaciated many times. The names of these glaciations – such as Tioga, Tahoe, and Sherwin – roll out over hundreds of thousands of years. Their remnants are beautiful. Glacial polish; deep U-shaped valleys; erratic boulders and moraines (which are carried miles by the ice and dropped on seemingly random plains and hilltops) are everywhere in the Sierras. Continue Reading →

Flying over California

I flew back and forth between Denver and San Francisco for an MIT field trip at the end of August 2015, when the western US was filled with smoke. The Utah and Colorado end of my flight is described in my previous post, which trailed off when Utah’s basins were lost from sight.

Here, we pick up again from San Francisco, crossing a beautiful, drought-stricken state. At San Francisco’s latitude, California can be easily divided into four regions running from north to south. The westernmost, and perhaps the most familiar of these, is the Coast Range. This includes the hills of San Francisco, which trap the city’s fog and keep it condensed around the bay in summer. Above the fog, these hills are golden.

California Coast Range

Continue Reading →

Climbing 2000m in the backyard of Santiago

The Andes are Santiago’s backyard, and Cerro Pochoco is one of the most accessible routes to explore them. This short (but steep) walk brings trekkers a spectacular 1100m (3600ft) above central Santiago, and the barren landscape offers spectacular views at every point.

This post will give a quick picture of the geography around Santiago, then an account of the trek. Directions to the trailhead, by car and by public transport, are at the bottom.

Mountains around Santiago

Santiago is a flat, 40km wide valley hemmed in on both sides by mountains. Last week, we visited the Cordillera de la Costa which separates Santiago from the sea. This week we go east into the Cordillera Principal, which is the edge of the Andes. All of these Cordilleras (kr-di-yeh-ruhs) refer to large scale mountain chains stretching hundreds or thousands of kilometers along the edge of the continent. The figure below shows a cross-section of the Andes (red line), highlighting the two Cordilleras and the Central Valley around Santiago. Map of Santiago Region with elevation profile

The Cordillera Principal is growing. At the edge of South America, two continental plates are colliding. The seam is a deep ocean trench 100km off the coast of Chile. There, the oceanic Nazca Plate is being subducted under the South American Plate. The force of the collision is buckling and thickening the South American plate to form the Andes.

The resulting uplift is large in geological terms: 0.3mm/year. In human terms, that’s an imperceptibly tiny number. That’s one skyscraper’s worth of height every million years. The construction of the Empire State Building was thirty thousand times that fast, and the Burj Dubai was fifteen times faster still. That’s something to remember next time your local contractors seem slow.

The Andes, however, are 100km wide and an unbelievable 7000km long. To lift an area that large, even by a fraction of a millimeter, means moving an enormous amount of mass. To use the skyscraper example, the Andes move the weight of about a million Burj Dubai’s per year (some of this is invisible under the surface). That’s something to remember next time a human city seems large.

Into the hills

I set out for Cerro Pochoco after a leisurely Saturday lunch. I took the Santiago metro, then the bus, and then walked for half an hour through the outskirts of the city between gardens full of aloe and flowering succulents.

Tiny lizard in the aloe

Finally, I reached a dead-end gate at a small astronomical observatory. A dusty, unmarked path curved along the wall and up towards the hills. I started up. The climb is steep, and I’m out of shape after living in Santiago’s smog. I was overheating in my T-shirt before I even set foot on the trail. Two birds of prey circled overhead and I wondered if they were waiting for me.

The rocks underfoot were a pleasant mix of volcanic flows, in different colors and textures, and volcanoclastics. Those are volcanic flows which picked up broken fragments of other rocks as they were deposited.

Volcaniclastics on Cerro Pochoco

The rocks here are some 25 million years old, which means they were laid down as the Andes were rising. Yet the forces which lifted them a kilometer into air have left surprisingly few marks. The bedding planes are all straight, with little visible fracturing or folding. The only evidence of the compression the region is experiencing are large, gentle folds on neighboring mountains. The picture below shows a 300m section of Cerro Provincia. Bedding planes are clearly steeply inclined on the mountain flank, but near-horizontal on the top, indicating that the mountain is formed by a large open fold. An open fold in the Andes

Rocks bend under pressure, like cloth or card. The greater the compressing pressure, the tighter the resulting fold. If the rock is strong (like card under gentle pressure), it will fold once with a consistent curve. This is what we see above. If the rock is weak (like paper), then under gentle pressure it may form many smaller folds. Rocks fold more easily when they are hot or buried deep underground. Since these rocks didn’t fold easily, we can assume that they were not deeply buried. This fits with their history. 25 million years ago, lava poured out onto the surface of Chile, one layer after another. As the Andes rose, they folded slightly under pressure. But that’s it. They weren’t buried or twisted along the way.

While thinking this through, I scrambled up to the summit of Cerro Pochoco (top photo). The hike up til now had been pretty. Here, it became spectacular. The glacier-bitten edge of Cerro El Plomo and the interior Andes began to peek out in the distance. The ridge ahead was blissfully flat. I spent a few minutes drinking tea and taking in my last sight of Santiago, then set off. The Cordillera is charming in winter. I walked in my T-shirt down a dusty, desert-like path with cacti at my elbows and snowy mountains on either side.

Cacti in front of the Andes

My target was a low peak at the end of the ridge. I had set myself a strict turnaround time of 5:45 to make sure I made it down before dark. With lots of huffing and puffing and a little bit of last minute sprinting, I made my summit at 5:44.

The view was thrilling. Unlike the mountains I’d been walking on, which had straight slopes and rounded ridge tops, the Precordillera has been glaciated many times. Its slopes are curved and its ridges are knife-edged. I marveled, and meditated… and then spent a happy half hour trying to take the perfect summit selfie.Perfect summit selfie in front of the Andes - Cerro Pochoco, Santiago de Chile

Do you think I got it? (Read on for directions to the trailhead) Continue Reading →

Climbing la Campana

In which I almost got lost in the Chilean bus system, then found my mountain again. It came with strange green rocks, adorable foxes, and great trekking partners.

We passed the day on the mountain’s summit, and never has time seemed shorter to me. Chile extends at our feet like an immense panorama limited by the Andes and the Pacific Ocean.” – Charles Darwin on La Campana

Few hills can offer as many views as Cerro La Campana, the ‘Bell Hill’. Its rocky summit looks west to the sea across Valaparaiso; south to Santiago, tucked in the misty Coastal Cordillera; and east into the Andes. Alongside its slightly tall partner, Cerro El Roble, it presides over a steep and ecologically diverse National Park. La Campana is one of the most dramatic day hikes available out of Santiago. However, hikers will have to be speedy to do it in time to catch the last bus home.

The trail rises by 1542m over 5.2km (non-drivers need to add an extra uphill kilometer from the nearest bus stop). Leisurely walkers can enjoy great views towards Valparaiso and the Cordillera de la Costa without summiting, however, or can camp overnight at the base of the trail and return in the morning. The best online route description is on Wikiexplora. I’ve posted a complete itinerary, with full details of public transport, at the bottom of this page.

Reaching the Parque Nacional

At about 8pm yesterday, I emailed six of my friends in Santiago to ask if they wanted to go climb La Campana. They all emailed back promptly to say that it was a great idea, then emailed again to say that I was absolutely crazy if I thought they’d all get up at six on a Saturday. I must have been crazy, because I did get up at six to catch the dawn bus to the mountain town of Olmue.

It was my first encounter with Chilean buses. Olmue is a two-hour drive northwest of Santiago, or forty minutes northeast of Valparaiso. I bought a return ticket, asked three ticket inspectors which bus stand was mine, and at caught my bus at 8:10. I saw that the bus had a little text-screen, assumed the driver would use it to announce the stops, and fell asleep. At 09:42 I woke up. All the nearby passengers were asleep. The little screen at the front of the bus blankly read ‘049km’.

Two stops went by, and two people went down past the driver and left the bus. I hadn’t a clue how they knew where they were. The windows were frosted white with condensation. I panicked, and at the next tiny stop I asked the driver, Cuantos minutos a Olmue? Plaza de Olmue? Siete, he replied. Just seven minutes? Back in my seat, I reached over my sleeping seatmate and rubbed the condensation from our window just in time to watch a tiny Olmue sign flash past. I got down at the next (and therefore westernmost) stop.

The bus disappeared behind me. The street signs around me had names not marked on my map. I gave myself fifty-fifty odds of being in the right town at all and started walking north. Continue Reading →

Hiking over glaciers in Skaftafell, Iceland

Skaftafell National Park (part of Vatnajökull National Park since 2008) is Iceland’s most popular national park after Þingvellir. It’s a six hour drive from Reykjavik along Iceland’s ring road. One of the park’s main attractions is Skaftafoss (shown at the top of the page and in my previous post on Iceland), a waterfall which runs down a beautiful wall of basalt columns. My group visited Skaftafell to hike, and to sight-see over a glacier.

Can you poke a glacier?

We camped just in sight of Skaftafellsjökull, a mile-wide tongue of the Vatnajökull ice cap. The camp was still closed for the winter, so this was a rather guilty affair. After pitching my tent, we took a twilight walk over to the glacier outlet. I had the naive idea that I could touch it, just to see what that much ice was like. We followed the campsite’s nature trail, which ended at a fence and a sign that warned us graphically of the dangers of quicksand. We were just in sight of what looked like a short ledge of ice. We would discover just how wrong we were the next day, when we climbed above the glacier. We hiked north-east and up. It was a beautiful morning. Glacier-carved peaks rose into the blue sky above us. Peaks above Skaftafell The afternoon, unfortunately, was a little less welcoming. As we neared the peaks seen in the photo above, the clouds descended. The trail had been marked with occasional wooden posts that stuck above the snow. These vanished. Continue Reading →

There might be bears

DSCF1768 Originally written for MIT French House (June 2013)

Well, this is embarrassing. I’m hiding behind a broken concrete wall. My rather muddy dog is taking an afternoon nap while I’m taking a chance to strip down to my sports bra, spread out my clothes to dry in the sun, and curl up barefoot on my backpack eating squished bread and tuna. It’s a peaceful chance to sunbathe – until a rather rugged man pulls up his pickup truck in the grass, not ten feet from me, and tries to turn it around. Oops. Should I grab for my clothes? Yell an apology? Nope. Just another hobo, he thinks, and drives off without a second glance.


It was a few weeks ago that I first had the brilliant idea of leaving behind my end-of-semester stress and taking some time by myself to think. I’ll take myself backpacking, I thought, I love hiking, it’s a perfect excuse not to do any work or check my email. I’ll do 100km or so for a little challenge. West Virginia isn’t that mountainous, right?

What I ended up doing was a fragment of something called the Allegheny Trail. I was accompanied by my dog Fei, who three days later has almost forgiven me for taking him on a never-ending-walk. It stretches some 330 miles through the Appalachians, and is the brainchild of a group of hikers who decided that if West Virginia didn’t have any long-distance trails, they would make one – an awesome attitude. Continue Reading →

A tale of two visas

I have a new game for you guys. ‘Where in the world is Kelly?’ I hope some of you are good at it, since I’ve begun to get rather confused myself. Set the clock to any time in the past week, account for jetlag, then throw a few darts at a globe between New England and Asia and you’ll probably be pretty close.
This summer I had a plan. I was going to go to Bangalore, and intern with Shell. I’d spend my weekdays working on computational fluid dynamics, and my weekends wandering on the roads and hills of India.

Lake at the botanical garden, Lalbagh, of Bangalore.
The red parts of the tree aren’t flowers, but leaves.

I was nervous, of course. How do I find housing in India? Can I haggle with autorickshaw drivers? Will I get sick? Will my work be interesting? What will I wear? Over a few days in Bangalore, I began to figure all of these out. Unfortunately, none of this may matter. Due to a certain miscommunication around visas, I showed up at work on Monday and was told in the early afternoon that I and another of the interns weren’t legally allowed to work for Shell.

Our Indian visas say ‘TOURIST’ on the spot where they ought to say ‘EMPLOYMENT’. This is a problem in spite of my offer to send home postcards from my cubicle and take smiling photos in front of the coffee machine. So, less than a week after arriving, with nothing but a single backpack full of paperwork and a change of clothes, I found myself back on a plane, going to New York to try to swap my visa.

The craziness.
In the past week, I’ve:
gone halfway round the world packed for the summer
learned how to haggle for hotel rooms in Bangalore
gone back with just a toothbrush, laptop and clothes
spent fifty hours in six planes and seven airports
straight into another four hours (so far) waiting in line for visas
to end up in a backpacker’s hostel in New York.
I should probably make it clear – I’m optimistic, though not 100%, about getting my visa sorted. My summer is not yet completely screwed, and MISTI and Shell HR are both trying to help.


That ordeal being outlined, here are a few fun thoughts on New York and Bangalore.

IMG_20140605_202859713_HDRMany of you are probably a bit familiar with New York. After living most of my life in places smaller than Boston, New York is exciting and a little overwhelming. It’s huge, it’s fashionable, it’s fast-paced and going everywhere at once.

Manhattan is packed tight with tiny shops and high rise buildings. You can buy postage, clothes, breakfast, passports, shoes and a dozen things you’ve never heard of on a single block. On a sunny green space a hundred feet wide and there will be fifteen people talking, twenty eating lunch and another five practicing yoga. New York has great plays and fancy museums. More generally, New York has a sense of newness – of modernity and power – that resonates with dreamers around the world.

Bangalore, on the other hand, radiates modernity and chaos. Square city blocks? Undeveloped green spaces? Construction that doesn’t block the sidewalk? Nah. Walking down a Bangalore street requires stepping over piles of rubble where the sidewalk has cracked, navigating street vendors, low hanging branches, and the motorcycles that take over the sidewalk whenever traffic gets too bad. In the street, autorickshaws and motorcycles pack in with cars and buses in a stream at least five vehicles wide on what the US would consider a two-lane street. Crossing the street is like wading through a  river river of metal and gas fumes.

Bangalore makes New York look underpopulated. Old. Even a little bit tame. Everything happens in New York, but in India everything goes out of its way to happen to you. Both cities have busy streets with all manner of people, but in New York you can walk with your head down and might make it a few blocks before being approached by someone, or smelling something, or stepping on something. In Bangalore, you get closer to ten feet.

Bangalore has bright colors and cows on the streets. New York has reliable electricity. Bangalore buildings are tattered concrete on the outside and gleaming metal on the inside. My New York hotel is gleaming on the outside and on the inside looks like Senior House but with more cats. Bangalore women wear beautiful saris; New York women wear neon with bared midriffs. I wear sneakers and just-off-the-plane-hair.

RxDx Cow (2)

Things that have happened to me in New York and Bangalore:
1. Asked for directions:                                                 NY 5,   BLR 0
2. Asked to take a photo for someone:                        NY 3,   BLR 0
3. Asked to let someone take a photo of exotic me:  NY 0,   BLR 8
4. Hopeful looks from street vendor:                            NY 12, BLR 40

City life
5. Things I bought:                                                           NY 40,   BLR 100
6. Minutes spent haggling for them:                          NY 0,    BLR 120
7. Minutes spent confused by transportation:        NY 120, BLR 45
8. Minutes spent confused by hotels:                          NY 10, BLR 240
9. Minutes spent confused by food:                              NY 20, BLR 30
Total time spent confused: 9h45 (It’s actually more than this. This is only the eyebrow-scrunching, map-checking, telling-three-concierges-the-same-thing confusion.)

Busy things
10. Fun conversations with a stranger:                       NY 3, BLR 1 (but lengthy)
11. Remarkably pretty plants:                                          NY 1, BLR 10
12. Bumped into a motorcycle:                                       NY 0, BLR 3
13. Bumped into by motorcycle:                                        NY 0, BLR 0 (phew)
14. Electricity failed:                                                         NY 0, BLR 30+
15: Offered cab/autorickshaw ride:                            NY 3, BLR 6
16: Sworn at by cab/autorickshaw driver:                     NY 3, BLR 1
17. Begged for money:                                                        NY 9, BLR 4

Weirder things
18. Offered weed:                              NY 1, BLR 0
19. Offered sex:                                  NY 2, BLR 1
20. Offered marriage:                     NY 1, BLR 0
22. Offered religious salvation:  NY 2, BLR 0

So, my advice for those of you thinking of going to new cities? Expect to be offered everything you don’t want, and confused about everything you do. But once you’ve finished scratching your head, and worrying about whether you packed shampoo – expect to have fun being surprised.

Marine fossils in the high Himalaya

“When the climbers in 1953 planted their flags on the highest mountain, they set them in snow over the skeletons of creatures that had lived in the warm clear ocean that India, moving north, blanked out. Possibly as much as twenty thousand feet below the seafloor, the skeletal remains had turned into rock. This one fact is a treatise in itself on the movements of the surface of the earth. If by some fiat I had to restrict all this writing to one sentence, this is the one I would choose: The summit of Mt. Everest is marine limestone.”
John McPhee, Annals of the Former World

Geology has given me a few moments that are nothing short of miracles. This was one of them.


This rock was picked up on Barucha-La, a high pass in the Indian Himalayas. It sits a thousand kilometers from the sea, and five kilometers above. It is ringed with the white fossils of ancient shellfish.

Iceland’s Golden Circle

Iceland’s Golden Circle is a popular tour through three of Iceland’s biggest attractions near Reykjavik. It’s an easy way to see some of the most dramatic scenery during a short visit. Some tour companies even operate directly out of Keflavik airport to serve tourists during flight layovers. The tour is also a quick showcase of the geological features which make Iceland unique.


Geological background: the skin and muscle of the Earth

We live on the Earth’s skin, which is called its crust. On the continents, the crust has an average thickness of 30km. That’s like having more than three Mt. Everests under your feet. It’s an enormous amount of rock by human standards, and if you live anywhere but Iceland[1] you can go your entire life without sensing anything underneath. 30km, however, is tiny compared to the 6371km diameter of the Earth. The Earth’s crust has roughly the same proportions as the skin around an elephant’s waist. The Earth’s muscle is hidden underneath its crust. This rock is denser and hotter than the crust. It moves with massive momentum and pulls the crust along with it. Currently, the Americas are being pulled away from Africa and Europe. On any map of the ocean floor, you can see a long ridge running the length of the Atlantic. At this ridge, the ocean floor is separating, and material from deeper inside the Earth is filling in the rift. The mid-Atlantic ridge runs directly across Iceland (red line in the image below). Major geologic features of Iceland The rock from inside the rift is called basalt. It’s a dark, dense rock found in many volcanic areas and all of the seafloor. It typically forms in volcanic eruptions and spreads away from its source in flat planar layers. These layers aren’t usually thick enough to build islands from the bottom of the sea, but in Iceland they had help. Iceland has a second source of volcanism called a hot spot. For currently unexplained reasons, hot material from inside the Earth jets upwards. It erupts in volcanoes when it reaches the surface, and in time these grow into basalt islands. The most famous hot spot is Hawaii. Under Iceland, the combined output of the rift and the hot spot built an island on a spot where the land itself is being torn apart.

Golden Circle 1: Þingvellir and the mid-Atlantic Rift

Our tour bus pulled up to Þingvellir (Thingvellir) on an uncommonly sunny afternoon with spots of March snow still on the ground. Þingvellir is one of the most dramatic sites of the rift, and its rough, vertical walls are truly unique. We were too stunned to absorb everything on our brief tour stop, and returned to camp in another of the National Park at the end of our trip. Many of the deeper rifts are full of water, making their depths impossible to guess. Their steepness is remarkable. In one place, I stepped over a narrow gap, then turned around and dropped in a heavy pebble. It was three seconds before I heard the splash. Photo of deep rift full of blue water.


Golden Circle 2: Gulfoss

The tour bus drove on, and our guide entertained us with Icelandic myths and stories of terrible trolls who ate misbehaving children in the night. I stayed pressed up against the window watching the cliffs and terraces that we drove past. In the introduction, I explained that basalt usually forms in flat layers after a volcanic eruption. Between lava flows, these layers are often covered by volcanic ash, tuff, or unconsolidated cinders called tephra. These materials are far softer than basalt. If a river erodes through a layer of basalt into soft tephra, it can continue horizontally without resistance through the tephra until it erodes the next basalt block. Sun, spray and snow came perfectly together for this picture of Gulfoss.. The falls were covered in frozen spray during our March visit, but it was warm enough for liquid mist to make a rainbow. On the right bank the ice highlights five distinct layers of basalt. The river has broken these into steps seen on the left.

Golden Circle 3: Geysir

Of course, you can’t have as much volcanism as Iceland does without some heat. After visiting frozen Gulfoss, we made a final stop at the boiling springs of Geysir. These springs are one of the more visible examples of Iceland’s geothermal resources. In addition, Iceland has many hot springs. Some are open to swimming, some are tapped for their power. As of 2010, over one-quarter of Iceland’s power is geothermal, as well as 87% of building heating systems. Many houses in the countryside have private pipes to bring in hot water for heating. The Strokkur geysir is very well-behaved. It goes off every five to ten minutes. Great Geysir itself has been dormant since an earthquake in 2010. Photo of Strokkur Geysir. The surrounding area is full of smaller water features and hot mud pots, such as the adorably-named ‘Litli Geysir’. Litli Geysir