Wednesday, November 27, 2013

What Creature of the Great Valley Could Have Snacked on Velociraptors? This one...

I apologize for the quality of the photographs today; they are from my phone, which is all I had when our latest display specimen arrived in our department. It's an exciting addition to the collection. We have been making a concerted effort over the last decade to raise the quality of science education in our impoverished community, an effort supported by our community with the passage of a bond act that brought about the construction of the Science Community Center at Modesto Junior College. The facility is wonderful, with a new planetarium and a fully operational observatory, as well as a vastly expanded Great Valley Museum.

My goal during this decade long project has been to increase the recognition that our county has a rich history of discovery in the field of paleontology. The first dinosaur ever found in California was discovered in our county in 1936. It was a hadrosaur, a duck-billed dinosaur, and we are still awaiting the arrival of a specimen of that creature in our department.

But what arrived today was one of the most fascinating creatures to ever come out of the sand and silt of the Great Valley Group: a mosasaur. The mosasaurs were some of the most fearsome sea creatures of the Mesozoic era. They were not dinosaurs, but instead were more closely related to large lizards. The middle skull is our recently acquired short-faced bear (Arctodus simus), one of the largest carnivorous mammals ever to exist, while the dinky little skull on the right is an accurately scaled velociraptor!
Mosasaurs arrived late on the scene, during the mid-Cretaceous Period, possibly occupying the environmental niche of the recently extinct Ichthyosaurs which had dominated the Mesozoic seas since Triassic time. Mosasaurs resemble varanid lizards (like the Komodo Dragon) and the various species ranged in size from about 10 feet (3 meters) to as much as 57 feet (17.5 meters).

The young man who discovered the first dinosaur in California, Al Bennison, also discovered the first mosasaur in our state. As it was an entirely new species, it was named Plotosaurus bennisoni. His specimen was probably about 30 feet long. Not long after an even longer species was discovered, Plotosaurus tuckeri, which measured over 40 feet in length.

I wanted a display specimen that could communicate to the young visitors in our museum and Science Community Center the excitement of the paleontological heritage of the region they live in, and having a four foot long skull of a mosasaur will go a long way towards achieving that goal. It arrived today and I was thrilled to see it. Just the same it was a terrifying creature. If it had you in its jaws, you weren't going anywhere. If you look in the picture below, you can see a second set of teeth in the back of the jaw. It was literally like something from the Aliens movies.

The specimen, from Taylor-Made Fossils of Missouri, is not a Plotosaurus, but will suffice to show what the Mosasaurs were like. The definitive source of information about the California mosasaurs is the book Dinosaurs and other Mesozoic Reptiles of California by Richard Hilton (who taught at MJC for a time; he is currently at Sierra College). The illustration below is a scan of his idea of the appearance of the Plotosaurus bennisoni.
From Dinosaurs and other Mesozoic Reptiles of California, by Richard Hilton

If you ever are passing through the Modesto area, be sure to stop in on the west campus of Modesto Junior College and wander through the Science Community Center. Even though the museum is not slated to open for a few more months, there are many other displays throughout the complex, including our new seismometer, and very soon, a mosasaur skull on the third floor in the geology area!

Tuesday, November 26, 2013

Where the Sierrra Nevada Rises From the Sea: A Quick Explore of the Monterey Peninsula

We've been exploring the most beautiful coastline in the world, and in the last post we were looking at a spectacular conglomerate, the Carmelo Formation, which formed in submarine canyons off the coast of California. The rocks exposed in the cliffs formed in the Sierra Nevada magmatic arc, but were sliced off and moved north along the San Andreas fault some 200 miles or more. Today we finish at Point Lobos and briefly explore part of the Monterey Peninsula.
The south end of Point Lobos includes China Cove and a beautiful sea arch with jade colored water. Jointing in the granitic rock allows the waves to exploit weaknesses to form coves, and arches can form along narrow headlands. Once formed the arches will increase in size until they collapse, isolating the headland as a sea stack or small island. It takes only a few feet of deep water to protect an island from terrestrial predators, so birds will nest there. In July the Brandt's Cormorants formed large groups that made me imagine penguins near Antarctica. The white bird droppings complete the illusion, resembling snow!

As we headed north along the highway, we encountered Seventeen Mile Road on the Monterey Peninsula. It is a toll road, passing through lots of private neighborhoods, but the appeal of the road is undeniable, so I will grant them a bit of free publicity. Where the cliffs at Point Lobos tended to be broken up by the stresses of nearby fault zones, the rocks on the peninsula are more solid, and wave erosion accents the joint patterns in the granitic rock.

Two unique species of tree grow on the Monterey Peninsula, the Monterey Cypress, and the Monterey Pine. Both of them have a very limited native range, the Pine in five groves along the coast, and the cypress in only two, at Point Lobos and Cypress Point on Seventeen Mile Drive. Although I refused to take a picture of it, a huge cypress on a headland along the drive is one of the most famous trees in the world. The poor tree has had all manner of wires and cables attached to keep the tree standing, and cement walls protect the base. I just sort of feel like the poor thing is abused, kept alive by extraordinary measures instead of letting nature do her thing.

The cypress trees, both alive and dead, make a marvelous counterpoint to the white granitic boulders along the coastline.

The Monterey Pine is the most widely planted commercial pine in the world. Some 10 million acres across the globe, especially in Australia and New Zealand, have been planted and are producing lumber. Most people would be surprised to learn just how limited the original forest is, just two islands off of Baja Mexico, at Cambria and Ano Nuevo on the California Coast, and on the Monterey Peninsula.

A large swath of forest has actually been preserved as a more or less wilderness grove, quite a surprise given the private landholdings. Developments still threaten the forest, but even worse is a fungus (pine pitch canker) that is killing large numbers of trees. It would be tragic to lose the trees, as the natural stands possesses far more genetic diversity than the plantings around the world.

The toll road climbs to a high point that offers views of the coast north of Monterey (when there is no fog). It was a pleasant drive through this uniquely Californian forest.

There is a fine description of the evolution of the Monterey Pine at http://evolution.berkeley.edu/evolibrary/article/montereypines_01, and an article on the Monterey Cypress at: http://www.pointlobos.org/nature/plant-communities/monterey-cypress-evolution. It makes interesting reading!

Up next: we jump across the Golden Gate!

Sunday, November 24, 2013

Need Geo-Pictures for that End of Semester Project? Check out Geotripper Images!

Active basalt lava flow at Kalapana on the Big Island of Hawai'i
Every so often I want to remind you all that I have collected a lot of my geology-themed photographs over at Geotripper Images (http://geotripperimages.com/). The pictures are available for free use in educational projects, either in student reports or by teachers in powerpoint presentations and the like. I would love to know that you've used a picture or two, and would even accept a tip, but the purpose is to be a resource. My only restrictions are if the photos are to be used in a profit-making enterprise, such as textbook photos or ads. Please contact me if you are interested in such uses.
Aerial view of Mt. St. Helens and Mt. Adams in Washington State
My whole reason for starting the Geotripper Blog six years ago was in part to make use of my burgeoning collection of geology-themed photographs taken during my journeys, and to telling the mostly geological stories of those journeys. After a few years, I realized the photos needed to be organized a bit more, so Geotripper Images resulted. A little research revealed that there are several other great geology photo sources on the net, so I linked to them in one of the boxes in the right column of the blog. Between Images and these other sites, you should be able to find pictures you need to finish that term paper on volcanoes, earthquakes and other earth science topics.
Saskatchawan Glacier in Banff and Jasper National Parks, Alberta, Canada
We've accumulated a few pictures of living creatures, so don't forget to check for animals that you might need. My work schedule means that additions are sporadic, but I'm intending to add a lot of shots in coming weeks as the semester winds down.
A normal fault in Mosaic Canyon, Death Valley National Park, CA
Writing this blog post reminds me of how lucky I have been to be able to explore as much of the world as I have. It's been a blessing, and I hope you enjoy the stories and the views. I also hope that you are encouraged to get out and explore a little more of the Earth that we live on. It is a fascinating place!

Have a good Thanksgiving holiday!

Thursday, November 21, 2013

Where the Sierra Nevada Rises From the Sea: Sea Wolves and Underwater Yosemites

Punta de los Lobos Marinos (Point of the Sea Wolves) is the source of the name of Point Lobos State Reserve, the next section of shoreline in our exploration of the most beautiful coastline in the world, the region between Big Sur and Bodega Bay in Central California. Point Lobos is one of the most popular of California's state parks, and so its inclusion in my little mini-series should be no surprise. Landscape artist Francis McComas once said that Point Lobos is "The greatest meeting of land and water in the world." I don't know that I completely agree, but that's only because of the nearby competition that I've already talked about in previous posts.

The sea wolves aren't land carnivores. The name instead signifies the elephant seals and harbor seals that frequent this section of coast. There have always been a few around when I've stopped in the area for a visit. And how ferocious they look!

There is a connection of sorts between seals (the Pinnipeds) and other large carnivores like the bears, canines, and felines. They shared somewhat of a common ancestry around 50 million years ago in a world much changed by the disappearance of the dinosaurs several million years earlier. Without major reptilian competition (although birds gave us mammals a run for our money), the mammals diverged quickly into several distinctive clans. Of today's carnivores they are most closely related to the bears or the Musteloids (otters, weasels, and skunks).
The title of the series invoking the Sierra Nevada grows from the realization that the rocks exposed along the coast in this region originated as granites of the Sierra Nevada Batholith. Subsequent shifts on the San Andreas fault system have carried these rocks, the Salinian Block, a minimum of 200 miles to the northwest, and possibly much more. In this sense, the Sierras do rise from the sea in the form of the Santa Lucia Mountains.

One of the wonderful features of the California Coast is how diverse the geology is. We've already seen in this series coastlines carved from volcanic rocks, metamorphic rocks, and granitic rocks. At Point Lobos there is something new and different: a colorful sedimentary conglomerate. The origin of the conglomerate allows us to draw one more comparison to the Sierra Nevada, although I admit the connection is tenuous one. Yosemite Valley is a deep 3,000 foot deep canyon with steep cliffs carved out of granite. Valleys carved in granite to depths of 5,000 feet with steep sides have also existed off the California Coast, and still exist today. They are not carved by glaciers, but by underwater landslides called turbidity currents.
Turbidity currents are masses of cobbles, pebbles, sand, and silt that break loose from the edge of deltas or continental shelves and flow as turbulent masses into much deeper water. Some turbidity currents travel at speeds of upwards of 50 miles an hour and as such have tremendous erosional ability. The Monterey Submarine Canyon offshore of California is as deep as the Grand Canyon, and is around 95 miles long.
55 million years ago, the Salinian Block was hundreds of miles to the south, and a submarine canyon was eroding at that time. The canyon filled in places with conglomerate and sandstone to become the Carmelo Formation which is found in exposures all around Point Lobos.
The pebbles include fragments of volcanic rock that  eroded from large volcanoes that once existed on the surface far above the deep masses of magma that made up the Sierra Nevada granites. I've never been much of a sedimentary petrologist, but I thought the conglomerates at Point Lobos were among the prettiest I've ever seen.
The sandstone exposures display interesting weathering patterns, like the cavernous weathering seen in the outcrop below.
And finally, a little biology. Not because I know what I was looking at, but because they seemed pretty.
There will be a bit more on Point Lobos in a coming post. If you want to visit, it is on Highway 1 a short distance south of Carmel Highlands. If you go, make sure to get an early start because the park is popular and the parking limited.

Tuesday, November 19, 2013

Where the Sierra Nevada Rises From the Sea: The Granitic Rocks of Garrapata State Park

We've reached the next beach on our exploration of the most beautiful coastline in the world, the one extending from Big Sur to Bodega Bay in Central California (register your arguments in the comments about your own interpretation of "most beautiful"!). It's called Garrapata State Park, and it offers some nice shorelines carved into the granitic rock of the Salinian Block, the displaced terrane of Sierra Nevada rocks that now forms a mountain range sloping directly into the sea.

Garrapata doesn't quite have the prominence of Julia Pfeiffer Burns State Park, or Point Lobos. There are no visitor centers and no campgrounds, and in fact, few tourist facilities at any kind. No parking lots or admission booths. Just a table or two and some fine trails. It is pretty much a wilderness park, aside from the intrusion of Highway 1.

The coastal terrace at Garrapata was covered in wildflowers despite the late season when we visited. Above we can see an Indian Paintbrush. I'd try to identify it, wondering if it was the rare Monterey variety, but became aware that with more than 200 species, I probably wouldn't be successful at nailing it down.

The rocky coastline reveals some of the best exposures of the granitic rocks of the Salinian Block. I use the term 'granitic' because the petrologists who study igneous rocks are rather specific when they classify the light colored grainy plutonic rocks that normal people call 'granite'. The proportions of the minerals that make up the rock (quartz, orthoclase feldspar, plagioclase feldspar) determine whether the rock is granite, granodiorite, tonalite, diorite and others. On this part of the coast, the rock is identified as the porphyritic granodiorite of Monterey. Granodiorite contains a higher proportion of plagioclase than granite has. The term 'porphyritic' means that the rock contains much larger crystals of feldspar in a finer matrix of other crystals,

The rock formed as molten plutons deep in the crust. The rocks cooled slowly over thousands of years, allowing the crystals to grow to visible size. The granitic rock is monolithic while it remains at depth, but when it is exposed by erosion, the release of pressure allows the rock to expand. It does, but not like a marshmallow. It breaks into vertical and horizontal fractures called joints.

Ocean waves do a great job of exploiting the joints and fissures, tearing the rocks up and producing rugged sea cliffs and offshore rock islands called sea stacks.When waves impact against the rocks, they can exert pressure on the order of several tons per square foot, and air is compressed in fractures to the same degree.

Waves can widen joint systems, forming sea caves, like those seen below.. I don't know how far the caves at Garrapata extend, but some on the north coast are hundreds of feet long, and navigable by kayak.


The kid in me wants so badly to explore caves like these. I don't think the California coast had much of a history with pirates, but I could imagine treasures being hidden in the backs of some of these caves.


Garrapata State Park also exposes an excellent example of a nonconformity. Unconformities of all kinds are buried surfaces where erosion once took place. A nonconformity develops when plutonic or metamorphic rocks are exposed at the Earth's surface by erosion. Later, the surface was covered with sediments, in this case conglomerate deposited by streams flowing across the coastal terrace. Wave erosion later exposed the relationship seen in the photo below.
Terraces are not especially common along the Big Sur coast, but a modest one can be explored at Garrapata. Terraces result when the back and forth of wave action on a beach forms a more or less horizontal wave-cut bench. If sea level falls or the land rises, the bench is lifted above the wave zone to form a flat surface surrounded by coastal cliffs leading down to the water below. The terrace was covered with colorful vegetation due to the stable deep soils.
It isn't maybe fully recognized by most tourists, but every sea stack and small island on the California coast is part of California Coastal National Monument, established in 2000 by presidential proclamation. There are around 20,000 such rocks along the 1,100 miles of the California shoreline!
Our last little discovery of the day was a small waterfall that developed where Soberanes Creek flows across the coastal terrace and trickles into small cove. It was a colorful intersection of rock, water, and life.

Next stop: the point of the sea wolves!

Addendum: one of my Facebook friends pointed out what a terrible name Garrapata actually is: Tick. It reminds me of Avenida de Las Pulgas near Menlo Park in the Bay Area: the Avenue of the Fleas. It's really true: all place names sound better in Spanish!

Saturday, November 16, 2013

It was the fault of no one, or maybe it's everyone's fault...the San Andreas and Calaveras faults in Central California

Central California has a lot of faults. One of them is a proclivity for bad geology puns. But it also has a great many exposures of active faults available for viewing in the space of an afternoon. The San Andreas, California's most famous fault cuts through the region, and the Calaveras fault lies a short distance to the east. It merges with the San Andreas north of Pinnacles National Park.
We became familiar with our faults today during our field trip between the town of Hollister and Pinnacles National Park in the California Coast Ranges. The faults are both actively creeping instead of building up ominous levels of stress. Earthquakes are a little bit less of a concern here, although some particular homeowners have problems with their foundations.
These are famous fault exposures. Photographs of these offset features have been published in textbooks all over the world. They are also easily accessible on public streets and parks. It is fascinating to watch the Earth in action.
The Calaveras fault is an offshoot of the San Andreas, extending north for about 70 miles from the vicinity of Pinnacles National Park. It has produced several magnitude 6+ earthquakes in the historical period, including a 1911 event in Morgan Hill with a magnitude of 6.5, and another quake in 1984 of magnitude 6.2.
A newly paved street at Dunne Park in Hollister
Dunne Park on Sixth Street in the town of Hollister is a good starting point to search out the fault zone. If you visit, please be respectful of the property lines. The people here see a lot of geology students, and while residents are almost always polite and even talkative, it would be sad to see "No Geologists Allowed" warnings springing up like "Neighborhood Watch" signs.
A short while later we headed south on Cienaga Road past the Hollister Hills Off-Road Vehicle park to the DeRose Winery. The warehouse was built directly on the creeping fault zone, and is slowly being ripped apart by the inexorable motion (two previous warehouses were apparently destroyed at this site as well). In the picture below, the cement wall was once connected to the wall with the blue tarp. They are offset by several feet. The dark plaque a bit to the left is a marker noting the establishment of the winery as a National Landmark.
The owners of the DeRose Winery are friendly and have never refused our students the opportunity to look at the fault damage in the building, even when important functions were in progress. They are to be commended for maintaining access to this important site.

The drainage culvert on the south side of the building is probably one of the most photographed fault offsets anywhere.
Our last fault feature of the day before arriving at Pinnacles National Park was a spot on Highway 25 where the San Andreas fault crosses the pavement. It has been patched many times, and in the last year or two, the highway was completely repaved. On our previous visit the road showed no evidence of motion, but this year we could see modest cracks forming.
I would have felt really bad if we had set off a major quake by jumping on the fault zone, but then again it sure would have been neat to stand on the fault as a large earthquake commenced.
Back to the beaches in coming posts!

Tuesday, November 12, 2013

Where the Sierra Nevada Rises From the Sea: Not the Easiest Beach to Find

A pleasant country road winds for a few miles through redwood forest and thickets of brush and poison oak to a secluded hidden beach. I've been through the region maybe a dozen times, but I never noticed the road branching off of Highway 1, and I usually traveled without detailed maps (really, can you believe THAT??). There are no signs, not even one giving the road a name (it's officially Sycamore Canyon Road for the record). Once you know it exists, it's not too hard to locate it, so I will leave you to your own devices on finding it for yourself.
In any case, there is a beach along the Big Sur Coast. That is actually rather extraordinary, given the way that the mountains rise from the sea. In most places there are steep inaccessible cliffs. Beaches can only form where sheltered coves allow sand to accumulate, sometimes at the deltas of creeks and rivers. The beach we are exploring today is Pfeiffer Beach, a section of coastline in the boundaries of Los Padres National Forest, but managed by the California Coastal Conservancy (I admit I've never understood how the federally-owned national forests of Big Sur were never made into national parks).
See? They really do welcome you to Pfeiffer Beach...once you find it.

There is a modest amount of parking available, and simple toilets (which is one of several possible explanations why the beach is so well hidden; it would be overwhelmed by crowds). The beach is just a few hundred yards down a sandy trail.
The very modest creek in Sycamore Canyon doesn't seem a likely candidate for producing enough sand to support a permanent beach, but some sand may be drifting along the coast from the north. The rocky sea stacks on the outer part of the beach provide an explanation for the accumulation of sand at Pfeiffer. They break up the wave energy so only relatively small waves ever impact on the beach. The sandbar is termed a tombolo, though it is not so perfect as to be a textbook example. A tombolo is a sandbar that connects an offshore sea stack with a coastline (look for a textbook example in a near future post).
The rocks include graywacke and metavolcanic greenstones of the Franciscan Complex. They formed in the guts of a subduction zone/trench system, and as such have been churned and mixed. The sea stacks are constantly pounded by the surf and have produced a group of sea arches visible from the beach.
The rock isn't right, but doesn't the shape of the hill in the picture below recall Diamond Head in Oahu, Hawaii? It's just missing a long string of high-rise hotels, and what a shame that would be here on the Big Sur coast.

From a more southerly vantage point on the beach, the tombolo is a bit clearer, connecting the sea stack on the left with the coastal cliffs on the right. The scrub covered slopes also hide some biological treasures (see page 18 of the road guide): the site includes the southern range limit for Little Sur manzanita, the rare Monterey Indian paintbrush (Castilleja latifolia), bear grass (Xerophyllum tenax); and the northern range limit for California peony (Paeonia californica). Not that I knew what I was seeing...

One more notable feature of Pfeiffer Beach is the purple sands. The beach sand is mostly composed of quartz, but streaks of the purple sand can be occasionally found. The color comes from the presence of grains of garnet in the sediment. I've now seen red, yellow, white, black, gray, purple, and green sand beaches.

See my previous posts for an explanation of the Sierra Nevada connection.