Scenes from a Superbloom (Part 2), and Evidence of a Snowball Earth (in Death Valley???)

Death Valley is a wondrous place at any time of the year, although it can be darned uncomfortable. There is value, however, in understanding the limits of human existence, which is something you indeed experience when the temperature reaches 120 degrees or so. I prefer visiting at times other than summer as a rule, and late winter is often ideal. We've been bringing students out here in February for more than a quarter century, and I never get tired of seeing this place.

 

But every decade or so, events conspire to turn a journey to Death Valley into something very special. The geology is always there and in your face (and in your nose, ears, and shoes). But if there have been a few precious rainstorms spaced just right in the fall, you can experience an explosion of life in the desert. Seeds that have lain dormant in the thin soils for years will suddenly germinate, and the barren rocks will be painted bright yellow, with lavender and white undertones here and there.

Beck Springs formation on the left, and Kingston Peak formation on the right.

We had driven just a few miles past Ashford Mill for a chance to look at some of the rocks from the earliest history of the North American continent. Around a billion years ago, an earlier supercontinent (called Rodinia, not Pangea) was stretching and started to fracture and break up. A series of fault basins developed in what is now Arizona, Utah, Montana, and here in Death Valley. Sediments filled the valleys, producing a three-mile-thick sequence of sedimentary rocks preserving several hundred million years of Proterozoic history (the time before complex multicelled life came to dominate the ecosystems of Earth). The mouth of the canyon below Jubilee Pass provided accessible outcrops of the three formations, the Crystal Springs, Beck Springs, and the Kingston Peak.

The Crystal Springs formation preserves ancient algal structures called stromatolites. They are the oldest evidence of life in California (but not in the world; life had already been on the planet for two billion years). The Beck Springs formation (in the dark hill below) is composed mostly of dolomite, which formed at tropical, even equatorial latitudes.

The presence of tropical rocks makes the Kingston Peak formation a real enigma. It's composed in part of a strange conglomerate referred to as a diamictite. The large boulders are in a matrix of muddy sediments such as one might expect to find on the ocean floor. The puzzle is: where did the large rocks come from? Big boulders don't usually get carried far out to sea unless they are encased in icebergs.

Icebergs? In the tropics? Even the most intense of the ice ages that we've studied from the last two million years never approached the tropics. They barely crossed the northen flanks of the United States. As evidence mounted, geologists started to realize the occurrence of an ice age more intense than any other ever discovered. The Snowball Earth hypothesis suggests that the entire planet may have been covered by ice around 700 million years ago, except maybe for a narrow strip at the equator.

We walked across the alluvial fan for a closer look at the Beck Springs and Kingston Peak rocks, but were distracted somewhat by the incredible flower display.

I got down on the ground and tried to get a few shots from a ground squirrel's point of view. If nothing else, the local rodents are able to  look around and say "salad" today!

The explosion of life on the barren desert floor was just stunning. These plants are supremely adapted to survive in this most harsh environment, and it was such a privilege to see it happening.

There were trade-offs, of course. The storms that brought the flowers also brought devastating flash-floods that destroyed roads. We couldn't visit some of our normal outcrops, so I had to redesign our itinerary for the next day. That led to a rather fine adventure, one in which we drove through a mountain range. That's "through", not "over". More in coming posts!

In Death Valley: What a Difference a Year Makes, What a Difference a Decade Makes

February 13, 2016

This spring is shaping up to be an extraordinary year for wildflowers at Death Valley National Park. There have been a series of wet storms (by Death Valley standards) and they have been spaced in such a way as to provide the best possible conditions for germination and growth of plants. Those who have visited Death Valley under "normal" conditions will have memories of barren rocky alluvial fans, naked slopes of bedrock, and a distinct lack of greenery. That most certainly is not the case this year. The wildflower show has started early, and it is robust.

We were in Death Valley over the weekend for our annual geology field studies trip, and one of our traditional stops is an exposure of the Pahrump Group of rock layers at the base of Jubilee Pass about twenty miles south of Badwater. The rocks record the ripping apart of the ancestral North American Continent around a billion years ago, and they are interesting no matter the season. The black hill is composed of Beck Springs formation, a dolomite deposited in a fault trough under tropical conditions. The orange rocks are the Kingston Peak formation, a rock that includes probable glacial deposits. In a tropical, even equatorial setting. These rocks record what may have been the planet's most intense glacial episode, a period when much of the Earth was covered by glacial ice (it's called the Snowball Earth Hypothesis).

But on Saturday, the hills and slopes were alive with Desert Gold and Verbena. And there were lots of green sprouts, promising even more growth in coming weeks. Officials are suggesting this might be one of the ultra-rare "superblooms" that occur over decades rather than years.

February 2015

Contrast the same spot as it appeared last year at the same time. We found a few flowers hidden in the washes, but clearly there was no explosion of life in that dry year in a place that is drier than anywhere else in North America.

February 2005

I've been privileged to see just a handful of extraordinary growth years. The only one I have digital images from was in 2005. It provides a nice comparison to what is happening in Death Valley right now. That year was a real challenge as we faced heavy rain and wind for most of the trip. The portrait below illustrates my morning observations that year. I'm thankful that we had perfect weather this last weekend.

I'm hoping to make a special trip out there in a few weeks to see how things are progressing.

Out of the Valley of Death: When a Broken-up World Turned to Ice

Our grand exploration of the Valley of Death took us briefly out of the valley itself where we could legally collect some Paleozoic fossils, and to do some training on outcrop interpretation (but no pictures of the Charlie Brown outcrop this year; see this for a previous year's version). We crossed Salsberry Pass at 3,315 feet, drove down a long drainage towards the south end of Death Valley, then turned north and crossed Jubilee Pass at 1,290 feet and drew close to Ashford Mill at sea level.

We were looking for evidence of the cold times in Death Valley. Not the cool times of the last ice age when a freshwater lake filled the valley floor. That was a blink of the eye in geologic time. We were looking at events nearly a billion years ago, when the continents of the world were breaking up, and the surface of the planet nearly froze over. Maybe completely frozen over.

Rodinia was a supercontinent that predated the better known Pangea. The break-up of Rodinia just prior to the beginning of the Paleozoic era heralded the appearance of complex multicelled animals on Earth, and the ragged torn edges of the continent here and there contain evidence of huge changes in world climate. The canyon below Jubilee Pass preserves the remnants a fault-controlled valley that developed along the margin of the newly formed Pacific Ocean and slowly filled with thousands of feet of sediment.

The rocks that filled the rift are collectively called the Pahrump Group, and are divided into three formations, the Crystal Springs Formation, the Beck Springs Dolomite, and the Kingston Peak Formation (oldest to youngest). The older two are interesting because they contain the oldest fossils known from California: structures in the mud that record the daily collection of mud and clay on algal slime that covered pebbles and boulders in a shallow sea that filled the fault trough. The concentrically layered structures are called stromatolites. But the Kingston Peak Formation is strange.

As can be seen in the picture above, the Kingston Peak is composed in large part of conglomerate, a rock with large numbers of boulders, cobbles and pebbles in a matrix of sand and mud. Most conglomerates form in alluvial fans or river channels, and much of the Kingston Peak seems to have formed that way. But some of the boulders show the scratches and grooves that indicate that they were dragged across a hard surface, and some look as if they were dropped into the mud of ocean floor. One of the few situations where this sort of thing happens is when icebergs melt and drop their load of boulders onto the sea floor. Such rocks of possible glacial origin are called diamictites

This would be pretty strange because the presence of carbonate rocks in the adjacent layers and reconstructions of continental distribution at the time suggests the Kingston was deposited in tropical or equatorial regions. No glacial episode in the last 500 million years covered that much of the planet. Not even close. It could be that these rocks at Death Valley formed in some other way, such as extensive mudflows or some other explanation. It's just that such diamictites have now been found at a few dozen places around the world, and that can't be ignored as a local circumstance. It looks like the Earth froze over around 700-800 million years ago. All the way from the poles to near the equator.

How could life on Earth survive such a calamity? Environmental refuges probably existed in the shallow oceans beneath the ice - cold, but not solid ice. Warm chemical-rich water could have been found in the hot springs around the mid-ocean ridges. There may have been freshwater lakes under the glacial ice. In any case, life had to adapt or die, and one of the strategies that evolved may have been multicellular organization and formation of tissues and organs. All complex life on the planet today may owe its existence to the "Snowball Earth".

The concept of a "snowball Earth" must still be considered an hypothesis. Although the glacial episode most certainly took place, many researchers feel that a strip of open ocean still persisted near the equator. Those details remain to be worked out. But on this day, we had a chance to walk across rocks that formed in a time when the Earth turned cold. Very, very cold. And we were observing those rocks from the hottest and nearly the driest place on Earth today.

We walked up a valley eroded along the boundary between the Beck Springs and the Kingston Peak Formations, and walked onto a ridge with a stunning view of the south end of the Death Valley graben. The high ridge of the Panamint Mountains rose in the distance. In the foreground was a black hill called Shoreline Butte, which would be our next stop. It was an incredible view, and it was an incredible story that was told by the rocks beneath our feet. We hiked back to the vehicles and headed up the road to Badwater.