Tuesday July 22, 2014, 49 miles (80 km) – Total so far: 3,033 miles (4,881 km)
I’m really not one for violence. You won’t generally find me watching movies starring Bruce Willis or playing video games like Mortal Kombat. However, there is a lot of violence in the landscape today, and the dynamism of that landscape is beautifully displayed at Craters of the Moon National Monument.
At first, the landscape appears very benign. The flat expanse of the Snake River Plain only has a very gentle incline as we ride west. It is so gentle, you don’t even really notice it. Far to the south, west, and east, the plain spreads out to the horizon. Remnants of volcanic activity rise in large buttes far to the south, and the Basin and Range mountains reach down in finger-like ridges to the north. But this landscape today does not immediately show the violence of its past.
I left the KOA just as the sun started to rise. My goal is to get out to the monument, 20 miles away, and have a good look around before the wind picks up and it reaches the forecast high of 93F. The shoulder on the highway is wide and good. I put down the miles as we cross the basalt flows.
The Snake River Plain is 30-60 miles wide and about 360 miles long. It stretches from Yellowstone to eastern Oregon. There are different theories on how it formed, but the most popular, recent theory is that the continent is moving southwest over a stationary mantle plume, or hotspot. The plume causes rhyolitic and basaltic volcanism. Some geologists speculate that there have been more than 7100 massive blasts and eruptions along the Snake River Plain in the past 17 million years through 7-13 overlapping, volcanic craters. Most amazing to me is the thickness of the basalt flows which have filled the old calderas and the path over the hotspot. That chunky, rough dark rock that stretches as far as you can see is thought to be 0.6 to 1.2 miles thick.
There are a series of hills that step up onto the end of the Pioneer Range as you close in on the national monument. The trucks rumble up slowly, twisting along the curves and disappearing over a distant hill. I’ve made good time getting out here and time it perfectly with the opening of the visitor centre. It is small and was built in the 1960s, but the exhibits are a good introduction to the landscape and events of the area.
There is a driving tour with quite a few short, interpretive hikes that you can take. The drive circles through the northern part of the monument and allows you to see most of the features associated with the eruptions here. It is not a flat ride, though, so expect to use a climbing gear at the beginning and to have a flying downhill midway through the loop. The spur road is fairly flat.
I start the day climbing to the top of Inferno Cone – a cinder cone created by explosive blasts and accumulation of volcanic material. The top of the cone gives a great overview of the Great Rift which is a series of deep cracks that stretch for 52 miles. The stretching of the crust that forms the Basin and Range topography to the south and north (which we viewed yesterday) triggers volcanic activity along the Snake River Plain. The stretching releases pressures on the hot rocks along the hotspot path and causes them to melt. The magma then travels to the surface along planes of weakness like the Great Rift. Lava fields which have poured out of the Great Rift cover 618 square miles.
The eruptions begin with a ‘curtain of fire’ – a long line of erupting fountains along the rift fissures which spray 100-200 feet into the air for days. Then, as vents become clogged, an explosive phase begins as the magma is forced through the constrictions. This can last for hours to weeks and creates the cinder and splatter cones and volcanic bombs (blobs of molten rock). Finally, as the explosive phase concludes, lava flows from the fissures. This phase can last for years.
There are three lava fields in the monument. These are made up of at least 60 lava flows and 25 cinder and spatter cones. These have formed along eight eruptive fissure systems aligned along the Great Rift. The field that the tourist road travels through is the ‘largest dominantly Holocene (last 10,000 years) basaltic lava field in the continental United States’.
The Great Rift flows and features began about 15,000 years ago. The average time between eruptions is 2,000 years. The last eruptions were just over 2,000 years ago, so the system is due to erupt again at any time. Interestingly, there is evidence through oral traditions and artefacts that the Shoshone’s ancestors witnessed the more recent eruptive periods.
To me, the most exciting part of this landscape is the convergence of so many pieces of time. Here you have a basaltic plain created over 17 million years as the continent moves over a hotspot. Overlain on that period is the crustal extension which has created the mountain ranges to the south and north of the monument over the last several million years. Overlain on that are recent events related to that crustal extension which has seen the Great Rift develop and spew out volcanic material starting 15,000 years ago. On top of that layer of time, you have humans moving through the landscape witnessing those eruptions over several thousand years. Yet another layer of humans, non-indigenous ones, have been travelling through the landscape in the past 150 years on trails of westward emigration. Then, finally, you have on top of all of that, an amazingly diverse collection of plants (more than 750 species) and animals (around 300 species) that have colonized and adapted to life in this harsh high desert and lava landscape. All of these layers of life and time are what makes my heart and head sing with joy.
I end up doing nearly all of the trails on offer, taking the time to examine all of the different features and attempt to understand how each was formed. I try to imagine the landscape as it was forming and think about what was happening at the same time in other landscapes I’ve travelled through on this tour. I am so impressed by the diversity of plant and animal life here, too. That was a bit unexpected.
I do not do the trail to the lava tubes, because this appears to be incredibly popular with families and as a way to get out of the heat. I’ve been in lava tubes before so don’t need to do it with a whole bunch of children under 12 years of age. It is still mid-afternoon, and very warm, by the time I make it back to the visitor centre. I go back in and look at the exhibits again to consolidate my learning. Then I go get two drinks out of the snack machine and drink them as I watch the introductory film (to again consolidate my learnings).
I hop back on the bike with a great tailwind and the knowledge that I’ve got a good downhill to start and a gentle downward trend all the way back to town. The wind gives me such a great push! I’m doing 25 mph down the hill with no effort. I do get one rather violent bit of excitement on this downhill, though. Off to the left, a dust devil that’s been travelling along the road changes course and heads directly at me. Crap! I’ve never ridden through one before. I can’t slow down or change course, so I just hang on. It is a swirling mass of debris that shoves me very hard to the right and then immediately back to the left. My eyes are closed through all of this because of all the dust and grit. It is abrasive on my legs. Wow! That was nuts! Thank goodness for the wide shoulder and enough fitness at this point in the trip that I could hang onto the bike really well! Riding through a dust devil is a first for me. The violence of it was certainly in keeping with today’s theme, however.
Somewhere along the way today, I’ve crossed the trip’s 3,000 mile-mark. To celebrate, I go to the supermarket (there is also a Family Dollar in town) to get food. They have a terrific sale on blueberries and strawberries, so I load up on protein, fruit and carbs and head back to the RV park to gorge myself. Another fine day done!