Tuesday, October 17, 2017

28th Anniversary of the Loma Prieta Earthquake - It Was a Warning That is Still Operative

What a different world... on Oct. 17, 1989, there were no smart phones, the internet barely existed, and we still depended on things like newspapers, television and radio to keep up with the world. Most of my current students had not yet been born, and that means that most of my students have never felt or experienced a major earthquake. Today we joke that when the BIG ONE hits, the tweets and Instagram posts will outrace the P-waves across the surface of the planet (there is a small bit of truth in the joke).

Earthquakes are not a joking matter though, and it is sobering to think that damage of a magnitude 7.8 quake in Los Angeles or San Francisco will have effects that will put California into a world of hurt not all that different than what is happening now in Puerto Rico or the Virgin Islands. Although we have had 28 years since our vivid warning in the hills above Santa Cruz, we are still not as ready as we should be, and many of our fellow citizens are complacent about earthquake safety. The ongoing experiences of hurricanes and wildfires across our country remind us of the importance of being ready with water, food, first aid, communications plans, and escape routes. As has been sadly demonstrated, we cannot depend on the federal government to act on our behalf in an effective manner, given the depletion of their resources following other major disasters, and stupid politics currently infecting Washington D.C.

I have yet to be in the middle of a major tremor; I've been on the outskirts of several, including 1989, and the 1971 Sylmar earthquake in Southern California. I was on the scene of the 1992 Landers quake (magnitude 7.3) within a week to see the ripped up ground. My experiences were mostly of the learning kind, not that of personal loss. Still, there is something to be learned in every experience. What follows is an abridged version of my story from a post on the 20th anniversary.
In 1989 I was a brand-new instructor at Modesto Junior College, in my third semester. I taught classes in the old 1950's-era Science Building on our east campus, up on the second floor. I had all the modern teaching technology; there was a chalkboard, and two television monitors hung from the ceiling for showing those newfangled "videotape cassettes". The monitors also served as my decidedly low-tech seismometers. They shook noticeably during the smallest of earthquakes (most memorably during a class test on earthquakes; no one but me even noticed).

On October 17th at 5:04 PM, my physical geology laboratory had just finished and almost everyone had gone home to watch the World Series. A couple of students were helping me (it was Maureen and Sonny; funny how I remember the names of the first students I had better than the ones I had last semester). We were 100 kilometers from the epicenter, so when the seismic waves started to shake our building, the movement was a strong rolling motion instead of sharp vibrations. We looked at swaying TV monitors, and commented that it was an earthquake. It was a most scholarly discussion, actually. We realized the shaking was not stopping, and we thought we could sense the direction of the quake as well. We started to guess where it might be happening, but when the shaking reached the 40 second mark (the energy was spreading out, it lasted only 10 seconds or so near the epicenter), we realized it was a major event, and that fatalities were probably occurring (and unfortunately we were right). The deodar trees out the window were whipping back and forth as if they were in a high wind. The strangest part for me was the unconscious decision I was making as the shaking progressed. Despite having a quiet scholarly discussion, my body was moving from the front of the podium to the back, where there was a nice solid space to hide under. I would have dived under if the quake had lasted any longer.
The Cypress Structure in Oakland where 44 people died

In hindsight, I should have been a bit more aggressive about taking shelter under the desk. An analysis of our building a year or two later revealed an architectural weakness that suggested the building could collapse if the seismic waves hit it from a particular direction. A seismic retrofit a decade later included some massive shear walls in the lab I taught in.

Meanwhile, at the city library, my children were making me proud. At the time of the quake, there were huge sailing ship models on display, in some cases right on top of the book stacks. The stacks were not reinforced or braced, so there was a real potential for injuries if the quake was strong enough to knock those stacks over. I was told that most people were just standing there watching the bookstacks swaying, but my kids, my well-trained and intelligent kids were the only people in the room to take shelter under the sturdy study tables. Luckily, as I said before, we were on the fringes of the effects of the earthquake and no one was hurt.

The Loma Prieta earthquake, a magnitude 6.9 event at a depth of 11 miles, was a tragedy: 63 people died, and 3,700 were injured. The Bay Area was in chaos for days and months passed before life got back to normal. We were on the fringes, so instead of pain and suffering, we had a profound learning experience that was remembered by my students for the next decade and a half. But it has been 28 years now, and as I said, many of my students weren't born when the quake happened. Few of them have felt a quake at all. The large quakes like Loma Prieta and Northridge are ancient history, and there is less of that innate knowledge of what they should do when one hits. Few admit to having any kind of emergency kits at home, and they have no plan for what to do when the next big one hits.

Fault studies across California make it clear that more big tremors are coming, almost surely within the next decade or two. We educators must keep these past events alive in the minds of our students so they will be ready for these events when they come.
I'm sorry I can't provide a source for these photos. They are scans from a slide set that I purchased many years ago, soon after the quake occurred.

Saturday, October 14, 2017

Feeling a Bit Sheepish: A Bit of Glacial Mutton in the Sierra Nevada

Pothole Dome in Tuolumne Meadows at Yosemite National Park
Sometimes glacial terms represent some kind of logical relationship to reality. "Horns" that are sharp pointed glacial peaks, "cirques" that are circular-shaped glacial bowls, "glacial polish" referring to rock worn smooth by glaciers, or "moraine lakes" that are lakes dammed by glacial moraines. Then there are the others: tarns, eskers, kettles, aretes, and cols, the kinds of terms that cause misery among my first-year geology students. But one term seems to depart from all reality...roche moutonnée
Unnamed roche moutonnée just north of Lembert Dome in Tuolumne Meadows
The term roche moutonnée describes an asymmetrical glacially scoured rock outcrop that has a smooth slope on the side facing the flowing ice, and a steep cliff on the side where the glacier pulled away from the outcrop ("stoss and lee structure" is a related term). The scale can range from a few meters to many hundreds. They are common features in regions of bedrock that have been scoured by massive continental ice sheets, but are a bit less common in mountainous areas eroded by alpine glaciers. These glaciers are the kind that filled valleys, but didn't overwhelm the surrounding peaks, such as those that flowed through most canyons of the Sierra Nevada. Yosemite Valley is the most famous, but glaciers filled dozens of other major river canyons from south of Sequoia National Park all the way north to the Lassen Volcanic National Park region. At their height, these glaciers covered about 30% of the mountain range.
Hiking the gentle slope of Lembert Dome in Tuolumne Meadows
The Tuolumne Meadows region of Yosemite National Park was an odd exception to the usual Sierra Nevada glaciers. The area surrounding the meadows was covered by a 2,000 foot thick mass of ice that was far more like a continental ice sheet than an alpine glacier. The ice spilled over ridges into several other drainages, including that of the Merced River, which carved Yosemite Valley. The addition of ice from the Tuolumne drainage gave the Yosemite glaciers an extra bit of "oomph", allowing them to erode deeper and farther than they would have otherwise.
Looking down the western edge of Lembert Dome. Note the glacial polish on the summit ridge.
There are numerous roche moutonnées in the Tuolumne Meadows area, including the easily seen Pothole Dome (first picture of this post), and Lembert Dome near the Tuolumne Meadows campground (below). The summits of each are easily climbed (from the right direction, anyway), and both provide stunning views of the region.
The problem with roche moutonnée as a geological term is that we geologists can only barely agree on its meaning. It's derived from French, and the "roche" part isn't a problem. It means "rock". But "moutonnée" is the tricky one. It can be translated loosely as "sheep" (think "mutton""), but not exactly (French: "mouton"). Moutonnée (with the extra e's) translates to "frizzy", and is taken as a reference to sheep's wool. The term originated in the 1700s with a naturalist named Horace-Bénédict de Saussure (it would be decades before the term "geologist" was coined) who noted that the rocks looked like a type of wig apparently well-known at the time whose locks were held in place with mutton grease. Except that there seem to be few or no references to wigs that were actually called that (the closest version was a tête de mouton).

So we teachers are left with trying to define the term as meaning "rock sheep" based on the nebulous idea that the rocks look like sheep grazing in meadows. Which they really don't. But it's still easier than trying to describe obscure French wigs from the 1700s and mutton grease.
A few weeks back we were on our field studies trip to the eastern Sierra Nevada, and we descended from Sonora Pass into the drainage of the West Walker River at Leavitt Meadows. I was describing various glacier features and even mentioned the presence of a few ill-defined roche moutonnées upstream of the meadow. You can see them in the picture below. But then I noticed something else in the midst of the meadow. I saw them, and now you are hoping that Geotripper won't go there, but he will...
Yes. It was actual....
...rock sheep! In a meadow.

But I still don't think they look like eroded glacial domes.

For an excellent description of the derivation of the geologic term, check out this great story from the Atlantic.

Thursday, October 12, 2017

You Just Can't Take Sonora Pass for Granite: Travels Around the Sierra Nevada High Country

Sonora Pass in the Sierra Nevada is a sort of forgotten step-sister of the more famous Tioga Pass in Yosemite National Park. A paved road, State Highway 108, crosses the crest of the Sierra about forty miles north of Tioga, cresting out at 9,624 feet, but it sees far less traffic. There are, for instance, no national parks, no major ski areas (Dodge Ridge is thirty miles to the west), and no major resorts, and snowdrifts keep the pass closed for much of the year. But Sonora Pass is an incredible place to visit if you ever get a chance, and it makes for a nice loop trip out of the Central Valley, including Tioga on the way back.
The road is steep and winding towards the top, but the views are extraordinary. We are in the headwaters of the Stanislaus River, and the region was heavily glaciated during the ice ages, making for spectacular alpine scenery. But one thing seems to stand out as one approaches the summit. You can't take this pass for granite. At least not all of it. This bad pun can be understood in two ways: there is volcanic rock at the top of the pass, not granite, and what "granite" there is along the lower reaches isn't actually granite.
First off, there are lots of fine exposures of granitic rock below the pass, and along the highway for a considerable distance downstream to the west. But it is not technically granite. If one has had a basic earth science course, a person may have learned that there is granite, diorite and gabbro as the plutonic igneous rocks (light, medium, and dark). But if one takes physical geology or an upper division petrology course, one finds there are other rocks intermediate between granite and diorite. The differences come from the proportions of potassium feldspar, plagioclase feldspar, and quartz. As such, true "granite" is actually somewhat rare in the Sierra Nevada, perhaps accounting for 10% of the total. The most common rock is granodiorite, a granite-looking rock rich in plagioclase, but lacking in potassium feldspar.
I'm the first to admit that the difference to a layperson may seem trivial, but recognizing these differences allows researchers to draw many conclusions about the circumstances and timing of the intrusions that formed the backbone of the Sierra Nevada. And some of the other
"granitics" are truly beautiful rocks. At Sonora Pass, the common granitic rock is called the granodiorite of Topaz Lake, and it is one of the younger intrusions in the Sierra Nevada, having cooled about 89-93 million years ago. It has massively large crystals of potassium feldspar, 2-3 inches long, embedded in a groundmass (matrix) of smaller crystals of quartz and plagioclase. Such rocks with two distinct grain sizes are described as porphyritic. Glaciers have smoothed off the rock in many places ('glacial polish'), almost providing the effect of a polished countertop.
The other way that Sonora Pass cannot be taken for granite is the fact that the rocks at the pass are actually volcanic in nature. Between 11 and 9 million years ago, this area was an extensive volcanic center broadly similar to the one that exists today at Lassen Volcanic National Park, with andesitic stratovolcanoes, lava domes, and a modest caldera complex.
The volcanoes are long extinct, and glacial erosion has greatly modified their original outline. The mountains are striking if for no other reason than that they are different from many of the light-colored peaks of granitic rocks seen elsewhere. In a sense, they almost seem somber and dark. John Muir would no doubt have seen their beauty, but probably wouldn't have been inspired to call them the "Range of Light".
If you ever want to brag about your hiking exploits, but just don't have the energy, you can go to Sonora Pass, and wander a few yards up the trail that crosses the pass going north and south, perpendicular to the highway. That way, when people ask what you did last summer, you can truthfully say something like "I spent a bit of time on the Pacific Crest Trail"!

If you long to spend time in the Sierra Nevada, and just can't fathom the thought of fighting the crowds at Yosemite Valley and other parts of the national park, give Sonora Pass a look. I'm pretty sure you won't be disappointed. If you need a guide, my colleague Noah Hughes and I edited a field trip guide for the region for a meeting of the National Association of Geoscience Teachers in 2012, and the book we published is for sale (details are here; all proceeds support the scholarship program of the NAGT-Far Western Section).

Thursday, October 5, 2017

Fall Colors in the Eastern Sierra Nevada!

We've returned from a field studies expedition to the eastern Sierra Nevada, and I can report that fall has arrived! We've had a very warm summer, and the heat waves continued into September, but then we had a sudden cold snap, and even some snow. Tioga and Sonora Passes briefly closed, but opened again in time for our trip. The aspens and cottonwoods have responded to the sudden cold conditions.

Our route took us over Sonora Pass, where fresh snow still lingered on the high slopes. It's a sight I'm not used to. We spent a lot of time in the Bodie area and in the White Mountains where there aren't many deciduous trees, but late in the weekend we moved into the canyons below the Sierra Crest.
One of the special places is Convict Lake, which is dammed by a moraine of the Tioga glaciation that ended about 13,000 years ago. Aspens and cottonwoods crowd the shoreline, providing vivid color.
On our last day, we took the June Lake Loop, and stopped to explore Silver Lake. The canyon of Reversed Creek and Rush Creek is a spectacular glacial valley with high peaks above, and a string of beautiful lakes.
As we wandered among the trees, we heard a rockfall on the slopes high above. It wasn't all that big, leaving little dust in the air, but it was exciting to listen to geology in action.
It's been a long summer, but the drought finally broke, and the forest was looking healthy. Our mountains might not have the color range of the eastern hardwood forests, but then again, those forests don't have the mountain backdrop of our beloved Sierra Nevada.

Sunday, September 24, 2017

Say Hello to California's New State Dinosaur: Augustynolophus morrisi

This one really got past me. I have to admit that the whole business of establishing a California State Dinosaur flew way under my radar. But it happened, Jerry Brown signed the bill, and Augustynolophus morrisi is our newest state emblem (along with our state fabric, denim). Although much of the attention on this Saurolophus species is directed towards two specimens found in the Panoche Hills of Fresno County in 1939-40, few people are aware of the story of California's first dinosaur discovery. It happened in 1936, and it was found in our own county of Stanislaus. I've written about this story before, so what follows is an abridged version.

OMG! Somebody caught Jar Jar Binks! Okay, not really. But what the heck is this thing?
This is a skull replica of Saurolophus angustirostris, a closely related species from Mongolia
Say hello (sort of, since my skull is a closely related species) to Augustynolophus morrisi, our newly designated official state dinosaur!

We have half a million people in our county, and I'm willing to bet that 99% of them don't know what it is or why it's important to them. Only one person got to be the first to find a dinosaur bone in California, and that was 17-year-old Al Bennison in 1936. He was exploring Del Puerto Canyon in the Coast Ranges along the western part of Stanislaus County looking for shell fossils when he found bones scattered on a slope. He showed them to his science teacher who reported them to the paleontologists at U.C. Berkeley. A year later Bennison discovered the most complete mosasaur skull ever found in California (see below). The mosasaur species even bears his name. It may not be much of a surprise that he went on to become a paleontologist. I had the privilege of meeting him in 1996, when he took us to his original discovery site, shown above.
The Saurolophus was one of the last dinosaurs that ever lived on our planet, one the last groups in existence when the gigantic asteroid hit the planet (or when the volcanoes blew, or whatever else did them in). They lived in the latest part of the Cretaceous Period, which is well represented by sedimentary rocks in our region. The rocks are marine in origin, which tend not to be good places to search for dinosaurs, but sometimes a carcass would float out to sea.
Source: http://en.wikipedia.org/wiki/Saurolophus

The creatures were gigantic, on the order of thirty to forty feet long, weighing several tons. They were plant-eaters, with teeth well-adapted to grinding twigs and leaves. Whether they swam or not has been a topic of discussion and debate. Some argue that they had few other defenses from predators, so that swimming was necessary to escape from being eaten. Others suggest that they lived in herds that provided protection.
Our skull collection is now a powerful tool for teaching the students in our region about the heritage of the land that they live on. In the picture above, one can compare the Cretaceous plant-eater with the skull of a Short-faced Bear, which lived in our area during the Ice Ages during the last two million years. It may have been the single largest mammalian land predator that ever lived, with a standing height of 11 feet. It would have made a grizzly bear look small in comparison.
The picture above shows our other recent arrival, the Mosasaur, similar to the one found by Al Bennison during the 1950s in the Coast Ranges just south of our county. It was not a dinosaur but was instead a seagoing reptile from the Cretaceous Period that may have snacked on sharks. It was around thirty feet long. It is probably the most formidable predator ever to inhabit our region.
To give a sense of scale, we have the Mosasaur nosing an Ice Age Sabertooth Cat skull (the cats weighed 700 pounds), and one of those wimps of the early Cretaceous, Velociraptor (which came out of Mongolia, not the Americas).

Dinosaurs certainly capture the imagination of our children (and not a few of our adults), and it is a good thing for our students to know that our county played an important part in the paleontological discoveries in our state. When students realize that one of their own (however long ago) made an important find, they also can visualize themselves as a paleontologist or geologist making important contributions to science.

Source: http://upload.wikimedia.org/wikipedia/commons/4/4b/Saurolophus_scalation.png

Augustynolophus has its own Twitter handle, so check out developments at https://twitter.com/augustynolophus/. The Wikipedia page has been updated as well. For the best source of information on dinosaurs and other Mesozoic reptiles of California, check out this book by Richard Hilton of Sierra College.

Friday, September 22, 2017

Liveblogging the Deluge: The First Day of Fall and a River Finally Returns to Abnormal

I was mistaken. Nearly two months ago, I suggested in a post that the abnormally high flows on the Tuolumne River were finally subsiding, and that the great flood of 2017 might finally be ending. This happened because I strolled along the river on a day when the output from Don Pedro Reservoir finally fell below 5,000 cubic feet per second, to around 1,500 cfs. That lasted for an entire day or two. The inflow at Don Pedro was still several thousand cfs, and the effort to build up some emergency flood storage space in the reservoir meant that they ramped up flows to 5,000 cfs, and that level continued for another seven weeks.
Source: https://waterdata.usgs.gov/ca/nwis/uv?11289650

I walked the river again today and saw something I haven't seen in nine months: a river at very close to minimum mandated flow. A quick check of the river gauge on the USGS site confirmed that the river was flowing at a mere 339 cubic feet per second. A look at the table above shows how the flow has been declining over the last week.
The CDEC site for Don Pedro Reservoir is even more informative, showing high flows throughout August and early September. Inflow to the reservoir finally dropped below 1,000 cfs about the 12th of September, and the outflow was then also lowered (about 1,500 cfs is diverted for irrigation which accounts for the discrepancy between output from Don Pedro and the river flow below LaGrange Dam where the diversions take place).

Source: http://cdec.water.ca.gov/cgi-progs/queryDaily?s=DNP&d=22-Sep-2017+20:14

Don Pedro Reservoir remains well above normal in water storage after an extremely wet year of precipitation. It presently holds 1.7 million acre-feet, about 84% of lake capacity, and 126% of normal for this time of year.

The floodplain is a different place now, compared to what it was a year ago. The biggest change is the vegetation. Hundreds, maybe thousands of trees and shrubs have been uprooted and washed away downstream. There are huge piles of branches and tree trunks across the riverbed. Other areas along the streambed have been washed clean of any vegetation at all, leaving vast tracts of barren gravel and pebbles. The invasive and damaging water hyacinth is gone, carried downstream in the many months of flooding. One can only hope that the seeds were carried away as well, although they probably weren't. I'll be pulling any hyacinth out of the river that I see in coming months.
The river is not back to normal, because "normal" disappeared more than a century and a half ago when gold was discovered upstream. The original channel and floodplain was upended in the search for the elusive metal. Trees and shrubs were removed, and every bit of gravel was run through sieves, longtoms, or dredges. After the search for gold ended, quarrying for gravel and sand took over, further altering the floodplain, ultimately forming numerous ponds fed by groundwater seepage.
These days, efforts are being made by organizations like the Tuolumne River Trust to bring about some sort of natural balance on this badly scarred landscape. Adjustments to the channel can help expose the gravel bars that salmon need to spawn, and one can hope that the fall run will be more successful than those of the last five years during the drought. Only the Merced River has a more southerly run of Chinook Salmon. At one time 130,000 salmon cruised the Tuolumne. In the last decade, the run has exceeded 1,000 only once (1,926 in 2013).
Walking the Tuolumne River Parkway Trail in Waterford. This is my backyard.

In the meantime, the flood of 2017 seems to finally have subsided. The river is back to abnormal, and we now await the new storm season. After a monster season in 2017, one has to wonder what the coming year holds in store for the river.

Thursday, September 14, 2017

A Salute to Cassini-Huygens and the Team Who Successfully Explored Saturn for More Than a Decade

Amid the stupidity emanating from Washington D.C. these days, depression can be a real impediment to a happy life. Other events unrelated to politics give me some sense of hope about the future of humanity, and one of those things is drawing to a close this week: the Cassini-Huygens mission to Saturn. It is one of humanity's greatest accomplishments, the extended exploration of another planet in our Solar System. I want to offer my congratulations and appreciation to the team that made this mission possible.
Source: https://nasa.tumblr.com/post/165331742919/cassini-spacecraft-top-discoveries
Have a look at this summary of discoveries from NASA; it has some astounding images.
This incredible mission resonates with me in a special way. I was a child of the 1950s, and the world and the Universe were different places in so many ways for a kid who was fascinated by astronomy. In particular, we barely knew more about our own Solar System than we did a hundred years earlier. We had made larger telescopes, but their effectiveness was limited by the disturbances in the upper atmosphere that distorted high magnification images. In those primitive years before the Hubble Space Telescope and the Voyager satellites, the science of astronomy was an exercise in frustration. I would head to the library week after week, checking out every astronomy book in the stacks, hungering to understand our own Solar System. 

Source: Unknown

How little we knew! Venus was shrouded in clouds. Mars had visible features, but they were unidentifiable from earthbound telescopes. Jupiter and Saturn had some visible cloud bands, but their moons were simple points of light. Only Saturn had rings, and maybe three divisions were visible. Neptune and Uranus were small disks, and diminutive Pluto was a dot of light. I wanted to know more!
The advances came so slowly (at least to this young growing child). The first satellite missions to Mars in the 1960s revealed surface features (and a lack of alien civilizations). Pioneer swept past Jupiter, but the camera on board was relatively primitive by modern standards. In the late 1970s, the two Voyagers began the grand tour of the outer gaseous planets. It was an excruciating wait as the small satellites passed first Jupiter, then Saturn, followed by Uranus and Neptune (years passed between each visit). Then, knowing the satellites had arrived, there was the excruciating wait for the pictures to be downloaded and processed. It was worth the wait. The pictures and data were astounding, revealing worlds never imagined by humans. The child in me was absolutely enchanted. But something still seemed to be missing.

The missions were all fly-bys. The trajectory was carefully planned to glean as much information as possible, but the satellites flew past their targets fast, and the numbers of pictures were limited by both time and technology. What was really needed was to insert a satellite in orbit, and that is a daunting challenge. The Cassini-Huygens mission accomplished that task in a spectacular manner. Check out the "ball of yarn" below...satellites can only maneuver to a very limited degree because of fuel requirements, so the crew had to aim the craft with an extreme degree of accuracy.
A computer-generated representation of all Cassini’s Saturn orbits -affectionately called the “ball of yarn” by mission planners. The time frame spans Saturn Orbit Insertion on July 1, 2004 to the end of mission on Sept. 15, 2017. Credit: NASA/JPL-Caltech

The pictures of the clouds and bands of Saturn are spectacular enough, but the real adventure of the Cassini-Huygens mission has been the exploration of the rings and moons of Saturn. Six new moons were discovered and named, bringing the total of known moons to 62, second only to Jupiter's 69. In essence, Saturn is a planetary system with one "planet" that is larger than Mercury.
This picture is not showing Mars, Venus and Earth orbiting Saturn. It's actually a view towards the inner Solar System from behind Saturn (which is hiding the Sun)
 George Lucas could barely come up with stranger moons for his Star Wars movies than the very real moons we have in our Solar System. More than enough of them are somewhat like our own Moon, cratered and "dead" (i.e. geologically inactive). But some are...very different. It turns out that Titan, the largest, has a thick atmosphere complete with rivers and streams, lakes and even a few seas. It rains and snows. That might seem a bit odd, since the surface temperature is hundreds of degrees below zero, but the liquid isn't water. It is made of hydrocarbons that on Earth would exist as gases like methane.
Saturn's moon Titan, complete with atmosphere, and shallow seas reflecting the sun.
Another major moon of Saturn, Enceladus, is even stranger, if that is possible. It's the brightest object in the Solar System aside from the Sun itself. The reason is ice. The entire crust of the "planet" is made of water ice, and it covers a "molten" layer below of salty water that may be four or five times deeper than Earth's oceans (Enceladus is much smaller than Earth, only about 310 miles in diameter).
Enceladus, the ice moon of Saturn. An incredibly deep ocean lies hidden beneath the icy crust.
The fractures and cracks in the surface, along with a relative lack of craters suggests the surface of Enceladus is tectonically active. It is simply one of the most fascinating "worlds" in our Solar System. And when I was growing up, all it was to us on Earth was a barely visible dot of light in our most powerful telescopes.
Enceladus and Saturn. Enceladus is the brightest object in the Solar System besides the Sun itself.
 Saturn is full of wonders and mysteries that are now becoming apparent to human beings for the first time in all our existence as a species. What a privilege to be living in a time when things like this can happen! And what a privilege and honor it must be to be part of the team that made the entire mission possible. And what competence! The Cassini-Huygens satellite left Earth nearly twenty years ago, and the moment it left, no repairs would ever be possible. When I consider how often my laptops and smartphones have to be replaced or repaired, just think what it means to be the inventor and maker of a complex piece of technology that has operated for twenty years with barely a glitch in performance.
Mima and Saturn
So what now? It's going to take years to interpret and present the scientific discoveries concerning Saturn, and the data will inform the objectives of future missions to the planet. But what to do in the meantime? Well, there's another really big planet out there, and a new satellite just arrived and started its explorations. It's called Juno, and the planet it is exploring is Jupiter. Jupiter has now had a number of fly-bys (Pioneer 10 and 11, and Voyager 1 and 2), and it also had an orbiter mission (Galileo). Galileo provided a treasure trove of information, and the Juno will be able to build on that (it also has a more polar orbit, providing views that the other missions could not). In other words, this very wonderful human adventure continues.
Titan and Dione with Saturn as a backdrop.
So thank you, and congratulations to the team that gifted us with the Cassini-Huygens mission to Saturn. Tomorrow, the Cassini satellite will plunge into atmosphere of Saturn at a ludicrous speed (echoes of "Spaceballs") of about 75,000 miles per hour and go out in a literal blaze of glory after 13 years of collecting data. It will be transmitting information right up to the final seconds of its existence. It was a job well done.