NPS Web Page Chronicles Yosemite Valley Rock Falls

Via Yosemite.blog.com, here is a link to a new web page on the rockfall history of Yosemite Valley. Besides a report on rockfalls in 2009 (there were 52), the page includes a wealth of links to other resources about mass wasting phenomena in the region. The map above chronicles the location of all the major rockfalls from 1857 to 2009.

It was a big year in the valley for this sort of thing. The Ahwiyah Rockfall actually changed the appearance of Yosemite as seen from the Wawona Tunnel and Glacier Point forever, and was the largest rockfall in 22 years. Luckily no one was hurt or injured.

The Geologist was Crying Inside....

First, a big shout-out to all the geoblogs out there who provided such first-rate coverage of the Haiti Earthquake over the last few weeks. I appreciate Chris at Highly Allochthonous and Stratigraphy.net for the feeds that got all the information in one place. I was participating in a community symposium tonight about the earthquake in Haiti and needed a powerpoint presentation in a hurry on the geology of the quake, and I found all the info I needed in a few minutes.

The presentation went pretty well. 150 people came out on a rainy Friday night and most stayed for the whole two hours. We had a historian who spoke about Haiti's difficult birth and the difficult conditions that have held Haiti back over the centuries. I was speaking on the geology of the quake, and the implications for a place like California, so towards the ending I tossed up the graphic shown above to see the relative scale of plate boundary relationships in the Caribbean and California. There is no direct correlation, with California part of the American mainland and Haiti an island on oceanic crust, but the idea of a complicated boundary of multiple strike-slip faults leading into a convergent boundary is valid.

It was the last part of the evening that got to me. On the one hand, I was talking to a bunch of Californians and Americans who were interested and upset about what happened in Haiti when the earthquake struck, but despite anything we could say, the country is still pretty much remote from our everyday concerns. On the other hand, three young women sat in the front row listening to our academic discourse. They are MJC students, attending under the auspices of the Cooperative Association of States for Scholarships, the goal of which is to prepare foreign students to return home with personal, academic, and technical skills which will enable them to continue growing professionally, share the benefits of their training with others, and make positive contributions to the development of their countries. Needless to say, these three young ladies were from Haiti. They had lost friends and relatives in the quake, and had to live in fear for days before finding out the fates of their own parents and siblings.

They spoke briefly to the crowd, telling of their pride in being Haitian, and showing pictures of the best of their country, the places of beauty and magnificence, many of which have been lost. I can't imagine what it was like for them; in this country for only a little over a year, learning English almost from scratch, and hearing of the devastation of their home country from afar. And then trying to describe their feelings to an audience of strangers. Sympathetic strangers, but strangers just the same. I tried hard to understand what it was like for them, but the best I could do was to try and imagine what it would be like if the if the situation was reversed. And I felt the tears...

Not to be cynical, but Haiti is going to be gone from the news headlines soon. Some Hollywood star is going to divorce another Hollywood star, or some pro athlete is going to do something stupid, or some politician is going to make some colossally hypocritical assertion. And our collective short attention span will wander to other places. Please don't let it happen. A donation that feeds a few people for a few days is wonderful, but we need to look to the future of the country, and the efforts to help Haitians rebuild an infrastructure that can support the people in the long run. Please consider donating to Habitat for Humanity or other groups that will be participating in the rebuilding of the country.

Friday Field Foto: A Field

A geology professor I much respected was famous for saying "I wouldn't just take you ANYwhere!", no matter how plain and uninteresting the site looked. Invariably, the story told in the drab rocks was far more interesting than the original view suggested, a phenomenon familiar to many of my geologist friends. So today, for all the places I take you on Geotripper, here is a plain and uninteresting...field.

It's not just any field, though. In three years, if the stars align correctly, this will be the Modesto Junior College Community Science Center, and it will be a wonderful facility for advancing the sciences in our educationally-challenged Central Valley of California. Besides housing the Chemistry, Biology, Physics, and Earth Sciences departments, it will also include an observatory, a planetarium, and the Great Valley Natural History Museum.

The project is being funded by our own community through a bond issue that was passed several years ago, and much of the credit for the design and impetus for the project belongs to some very talented and tenacious people in our division. It's going to be a great facility! Construction bids are coming in at the end of the next month, and construction should begin soon after. Expect to see some updates as the building grows.

The Other California: A Mystery Solved, and One of the State's Prettiest Little Waterfalls

Monday's post was a bit of mystery, in that a dry channel turned into a rushing stream in less than a half mile. The answer is sort of mundane, but quickly leads into the story of one of the finest, most attractive waterfalls that I know of. It's on a lot of postcards, but I don't think many visitors from outside of the state know much of it. Welcome to McArthur Burney Falls State Park, the second oldest state park in California.

At the hard to define boundary between the Modoc Plateau and the Cascades provinces, basaltic lava flows are interspersed with lake sediments, and a series of fault lines cross the region. Basalt lava contracts as it cools, forming numerous fractures and joints that provide an avenue for surface water to sink into the ground. Consequently, streams and rivers can disappear and reappear in unusual places, sometimes in spectacular manner. Some of the largest springs in the country are found nearby (At Fall River Mills, a group of springs have flows of around 1,400 cubic feet per second, an instant river). Another spring rises on the Burney River (below), forming the river of our little mystery. It's what happens just a short distance downstream that makes this place special.

The water spills over a 129 foot edifice, which in a state that has dozens of high waterfalls might seem insignificant.

From farther back, we see that the water splits into two channels, but we also see that something is going on below the rim. Some of the water is coming is flowing out of the cliff face itself. In fact, a lot of it, perhaps more than is spilling over the edge.

The lip of the fall is a basaltic lava flow. The rock beneath the cliff is much softer, consisting of clay-like diatomite and volcanic breccia. The groundwater can't sink through the underlying layers, and is forced to the surface just under the basalt rim. It makes for a unique sight.

A short trail descends to a deep pool at the base of the falls, and provides another perspective. The amount of water is stunning. The flow of groundwater at the falls is far less affected by seasonal differences in precipitation, so the discharge remains fairly constant all year. If you are visiting California in the late summer, McArthur Burney is a dependable place to see flowing water.

My only (mild) complaint about the falls is that the basin opens to the north, so the sun doesn't shine on the falls much, except maybe mid-day (when I never seem to be present). Photographers do pretty well catching rainbows in the spray rising over the falls, but at the base, pretty much everything is in the shadows. It's a cool place to be on a hot day, but difficult to photograph (at least for amateurs like myself)!

The park offers a nice campground, incredible fishing, and a nice network of hiking trails (the Pacific Crest Trail passes through the park). Information can be found in the park brochure. The California state budget crisis threatens the park's future. For info on how you can help out, check out the California State Parks Foundation. The parks don't deserve to be constant budget footballs; please get involved!

The Other California: A Monday Mystery (and a gratuitous cute deer picture)

Today's entry into the Other California series lies in the Modoc Plateau/Cascade Provinces, and presents itself as a bit of a mystery...

How is it that this dry creekbed...

Becomes this river, less than 1/2 mile downstream?

There are no tributary streams. There aren't any storms in the area. The elevation is about 3,000 above sea level. An inadvertent clue of sorts is buried in an earlier post, found here.

This river is related to one of the prettiest sights in California that is not part of the National Park System, although a visiting president once called it one of the natural wonders of the world.

Oh, and here is your gratuitous furry creature picture for the day. I saw them along the upper dry creek while trying to avoid stepping into the prevalent poison oak.

The Other California: Five for the Price of One

The Other California is the story of the places in the state that aren't found on all the postcards. I'm finding some subject material in the familiar places that turn out not to be so familiar. Mt. Shasta is an example. The mountain is one of the most famous sights in the state, and people come to the mountain for many reasons: contemplation, climbing, skiing, hiking, and searching for errant Lemurians and Atlanteans. Everyone seems to refer to Mt. Shasta as a single mountain, but a brief look at the peak shows it to be actually five distinct volcanoes.

Mt. Shasta is often referred to as a stratovolcano, due to the alternating layers of volcanic ash and andesitic lava flows making up the structure of the mountain. It is often compared with symmetrical cones elsewhere in the world, such as Fujiyama in Japan and Mayon in the Phillippines. A different term, composite cone, is probably more descriptive. At least five major cones make up the edifice, erupted at different periods over the last 600,000 years.

The two youngest volcanoes, Hotlum Cone and Shastina are the most obvious of these multiple cones. Shastina, at 12,330 feet, is technically the third tallest volcano in the Cascades even lumped as it is with Shasta (it is the prominent peak on the left side of the photo above). It erupted during a series of eruptions around 9,800 years ago.

Hotlum Cone, the highest summit of the volcano, began erupting about 9,000 years ago, and has erupted numerous times since, including a possible eruption only 200 years ago. It is the most likely source of renewed activity on the mountain.

A drive to the end of the Everitt Memorial Highway at Panther Meadows provides a look (above) at two of the older cones. From the parking area Hotlum Cone is not visible. Instead, the upper flank is Misery Hill, and the jagged peaks to the right are Sargents Ridge. The Misery Hill Cone began erupting around 50,000 years ago, while Sargents Ridge is closer to 200,000 years old. Both cones are deeply scored by glacial erosion, and retain little of their original shape. I've outlined the cones in the photo below, including an approximate guess about the location of the Sargents Cone summit (note the slope of the layers).

The fifth volcano is the most enigmatic of all. It pretty much doesn't exist. The mountain developed prior to 360,000 years ago, but for a long time, no one knew where it went. Erosion could explain why it is gone, as could a massive explosion. It wasn't until 1980 that the actual explanation became apparent.

There is a vast area of knobs (called hummocks), small valleys, and ponds extending for 28 miles north of the volcano, almost to the town of Yreka. Geologists didn't quite know what to make of it, and it was mapped as a cinder cone field, which strangely had a consistent composition. Then Mt. St. Helens happened.

The St. Helens eruption was precipitated by an earthquake that shook the north side of the mountain loose into the largest debris avalanche ever witnessed by human beings. It traveled twelve miles down the Toutle River valley, and produced a unique topography: hummocky. As the dust settled at St. Helens, geologists knew they had an explanation for the strange landscape north of Shasta. Between 360,000 and 300,000 years ago, about 11 cubic miles broke loose from the volcano and flowed 28 miles, more than twice the distance of the 1980 event. So far as I know (I'm open to corrections), it remains the largest landslide known in North America.

The hummocky avalanche is visible in the aerial photo below (another view can be seen in one of my earliest blogs here).

The Other California: A Land of Fire and Ice (but mostly ice today)

I'm breaking my own rules here. My latest series is exploring the places in California that aren't on the postcards, but are worth a visit. The thing is, Mt. Shasta is one of the most familiar sights in the state of California. The gigantic stratovolcano, the largest of its kind in the Cascades Province (and one of the largest in the world) reaches an altitude of 14,162 feet, and can be seen from over a hundred miles away in some directions. It's on a lot of postcards. But most people see the volcano on their way from California to Oregon along Interstate 5, and in doing so have a hard time seeing one of the most remarkable things about the volcano that isn't volcanic.

California, the sunny, mostly arid, almost semi-tropical state is not known for its glaciers, but it most certainly has them. The Sierra Nevada has between a dozen and several dozen glaciers, depending how one defines them. The largest Sierra glacier lies beneath the peaks of the Palisades, and is a mile wide and half a mile long. But farther north, Mt. Shasta has at least seven, including both the longest, and the largest glaciers in the state. They are most easily seen from viewpoints along State Highway 97 between Weed and Klamath Falls, Oregon.

Whitney glacier is the longest glacier in the state, with a length of about two miles. It is also the only valley glacier in the state. It zigs, then zags down the center of the photo above. Most all the other glaciers occupy the cirques at the head of glacial valleys. Whitney displays many classic glacial features, including bergshrunds, ice falls, crevasses, and moraines.

Whitney is the longest glacier in the state, but it is fairly narrow in its valley. The honor of the largest glacier in the state is nearby Hotlum Glacier, which coats a slope on the northeast flank of the volcano. It is about 1.3 miles long and 0.7 miles wide. In the picture above, Hotlum can be identified from the rounded cracks (the bergshrund) on the left flank of the volcano. Bolam Glacier is in the center of the photo, and bits of Whitney are on the right.

The glaciers of Shasta have a unique distinction: they are one of the few glaciers in the world that are actually growing in size. Before any global warming deniers get excited, the growth is actually a consequence of the rise of world temperatures. Warming of the northern Pacific is causing an increase in evaporation, and is increasing the amount of precipitation on the mountain. The increase of snow is able to offset the loss of ice due to melting during the 1.8 degree Fahrenheit rise of average temperature in the region over the last century. Continuing increases in global temperatures will eventually overwhelm the glaciers, and they will most likely be gone in a century or so.

See them while you can!