Sunday, August 20, 2017

Notes From the Eclipse Trail (with apologies to Ken Burns)

{Note: This may not work right unless as you read you hear the voices narrating a Ken Burns documentary, like the Civil War, or Baseball...}

Dearest Ones...

It is August 20, 2017. I pray that our missive arrives intact from the hinterlands of the Oregon Territory. Our journey has been long and arduous, and the outcome remains a great uncertainty. As you no doubt recall, we left the familiar fields and cities of our Central Valley home a week ago, but the time might as well have been a year. We are tattered and dirty, but we remain resolute in our goal of witnessing a total Solar eclipse.

Our progress slowed as we entered the great forests of what the local inhabitants call the "Redwood Trees". The trees were immense, and the forest dark. It was hard at most times to even know the location of the Sun in the sky above. We pressed on, looking for some kind of shelter or inn that would take us in for a night. We found accommodation at an outpost called Albee Creek, in the deep forest of Humboldt Redwoods State Park. We found ourselves surrounded by wagons once known to us as VW Microbuses. It was an uncomfortable and worrisome night in the dark forests, as we listened to the sounds of men, beasts, and air-cooled four stroke engines.
We explored this strange new environment following the mere traces of human pathways, which we found to be covered with potholes and twisting and turning through the forest in confusing fashion. Navigation by the sun or the stars was well-nigh impossible, as we could not see them through the forest canopy above. We did our best with tattered maps provided by the local constabulary called "park brochures".
We have been set upon by the beasts of the forest, who seem to track our every move. The night was filled with the rustlings of animals large and small. There was the snap of branches, the snuffling of noses, and the munching sound of apples being consumed nearby. We even witnessed one of the behemoths high in an apple tree, stripping it of its bounteous fruit.
It was becoming clear to us that the eclipse would never be visible to us in the deep forests of Northern California, and so we set forth with few provisions and even less knowledge over the borders of the land called Oregon. At first little seemed to have changed, but as we continued further into the wilds, we saw that the inhabitants of the land of Oregon were different. As we stopped to refuel our conveyance, we were not allowed to handle the mechanism for pumping the petrol. It was done for us, but not out of human kindness. It was because of statutory decree. What kind of tyrant controls these poor inhabitants?
Still, we pressed on deeper into the land of Oregon. We realized that our hope of witnessing an eclipse would require more open lands, so we worked our way down to the coastline where the restless waves lashed at the solid rock in a mighty conflict. Eventually we arrived at a small village called Florence, where we found shelter with some of the locals. They are a kind people, and generous in their sharing of their meager resources of ribs and Chinese cuisine. We have benefited from their generosity and have regained strength for the journey ahead.
There are rumors passed around the local peoples of the days ahead of giant crowds, clogged highways, and high costs of parking. We fear for the future, yet we face it with a steadfastness that grows from our intense desire to see the incredible event high in the morning sky of August 21st. From our base camp, we sent an exploratory party in search of potential viewing sites, and there is a discovery of potential spots in the coastal areas with such names as Waldport, Seal Rock and Forfar. Our strategy and only hope for success is that we can arise before the sun itself and set out for these choice viewing localities. And so it shall be done, and only Providence knows whether success can be had.
As for myself, dear ones, I press on. I am covered with scrapes and bruises, as I may have misinterpreted the advice of the sages, and put on the eclipse glasses a bit soon. I have been walking into trees and walls at a horrendous rate and our medical supplies are running low.

But through our trials and troubles, the goal remains true and we hope attainable. It is known that no American can hope to see such a spectacle on American soil again before 2024, no matter their bravery and skill. We can only hope to press on with fortitude and stubbornness born of being earth scientists and astronomers.

Yeah, we'll let you know if we make it...

Monday, August 14, 2017

What do Bears Do in the Redwood Forest? They Eat Apples...

California is the only state whose state designated mammal is extinct. The last California Grizzly Bear died in the 1920s. But we do have bears, but they just aren't quite as terrifying as an angry Grizzly. The only bears native to California today are the Black Bears, a species found all across North America. Those in the east tend to actually be black in color, but out west there tends to be more variation, from black to almost blond.
It's usually terrifying for people to see a bear for the first time when they are out camping or hiking, but California bears are fairly benign. They got kind of a fearsome reputation as car destroyers in Yosemite Valley, but an intense effort by rangers to train tourists has largely brought the problem under control. The bears are certainly a nuisance in some environments where natural food is scarce (especially during the recent drought). But my understanding is that Black Bears haven't killed anyone in California in a century, although I'm always open to correction (I've heard of one or two deaths in Wyoming or Montana). We unfortunately kill bears instead, either on purpose or by accident. If you are driving in Yosemite National Park and see a temporary sign that says "Speeding kills bears", it means that a bear died at that spot.
I'm out on my last journey of the summer, headed towards Oregon hoping to see the eclipse, and we spent a few nights camping at Albee Creek in Humboldt Redwoods State Park. It's a nice campground, too small for large RVs, and off the main highway. It's next to a meadow that was a homestead a century ago, and a large apple orchard still survives. The bears not too surprisingly love apples, and actually ignored the campground in favor of a few tasty treats from the apple trees. They've already stripped away the low-hanging fruit, so getting some required climbing into the trees. Most of the campers weren't even aware that there was a bear only a few hundred feet from their campsite. It was a pleasant way to spend the evening, watching bears be bears.

Yes, I got a bit of video too....

Friday, August 11, 2017

After the Disasters that Formed the Crater Lake and Crooked River Calderas, St. Helens was Hardly a Blip...Right? Uh, Right?

Yup, perspective is everything. I've been going on for several posts about prehistoric volcanic eruptions that were pretty much unimaginable in their violence and destructiveness. The Crater Lake eruption took place 7,700 years ago, and put 15 cubic miles of ash into the atmosphere, covering much of the western North America. The Crooked River Caldera dwarfed the Crater Lake event, with something like 200 cubic miles of ash. A repeat of either event would result in a huge death toll, and a serious threat to civilization. Luckily, such events are relatively rare in the time frame of human history.

Which brings us to the next destination from our field studies journey through the Pacific Northwest last June: Mt. St. Helens in southern Washington. Every school child for the last 37 years knows the familiar profile of the mountain as it exists today, and vaguely knows that it looked much different prior to 1980. It appears in pretty much every science textbook in the United States, being the last volcano to erupt in the lower forty-eight states.
Mt. St. Helens prior to the May 18, 1980 eruption. Source: U.S. Geological Survey

The problem these days is that for many people, St. Helens is ancient history. It is a geological event that took place years before they were born, and as such there is a disconnect regarding the reality and intensity of the events that took place in 1980 and the years following. I'm even guilty of belittling the event by comparing it to the prehistoric eruptions that happened in the region thousands and millions of years ago
Mt. St. Helens in 2002. Note the lava dome in the crater interior
The eruption of Mt. St. Helens may not have been on the scale of Crater Lake or the Crooked River events, but it was a huge event, almost beyond imagination, by any kind of human standard. What had once been a mountain nearly 10,000 feet high was reduced to a smoldering crater 1,300 feet shorter. The trigger that led to the disastrous explosion was the largest mass wasting (landsliding) event ever witnessed by human beings. And many people lost their lives, despite the evacuation and relative remoteness of the mountain.

The eruption began in March of 1980 when a moderate 4.1 magnitude earthquake shook the mountain, the largest ever recorded. Geologists were concerned and wired the mountain with whatever sensors they could think of. The rising mass of magma began to interact with groundwater and ice within the mountain, and a series of ash eruptions tore away at the summit of the volcano. The magma began to push outwards on the north flank of the mountain producing a 600 foot high bulge. Geologists were concerned about slope stability, but what happened was far beyond what they expected, or could even imagine. On May 18, 1980 at 8:32 in the morning, a magnitude 5.1 earthquake shook the bulge loose in a titanic debris avalanched that dwarfed any ever seen by humans. It thundered down the north flank, partly into Spirit Lake, with the remainder shooting down the Toutle River valley for 12 miles. Twelve miles.

The loss of the bulge meant that there was no longer any pressure holding back the gas-rich magma chamber, and it exploded with the power of hundreds of atomic bombs. The main blast was directed north and west, again towards Spirit Lake, and down the Toutle River valley. The ash was moving so fast (around 300 mph) it actually passed the fast-moving debris avalanche, so that in places the ash layer is actually covered by the avalanche deposits.
Mt. St. Helens in 2006, during the eruption that began in 2004. Note the second dome in the crater, behind the first.
The ash traveled north at hurricane speeds, up and over the intervening ridges, ultimately traveling around fifteen miles. The heavy dust-laden air downed nearly every tree in its path, stripping away branches and bark. Unless they were already underground in burrows, no animals survived in the main blast zone. The total area of devastation was around 150 square miles.

USGS geologist David Johnston, monitoring the volcano from an observation station on the ridge that now bears his name was one of the first people killed by the blast. Despite the evacuation orders (which were not far enough away from the volcano anyway), 57 people died.

These are just numbers, and numbers can't always describe the totality of the destruction of this volcanic eruption. You pretty much have to stand in the middle of it, and walk it. My first exposure to the devastation came about dozen years after the main blast (smaller-scale eruptions continued through 1986). I drove to the Windy Ridge Observation Point on the east side, which at the time was the only real viewpoint. The mountain was socked in by clouds (I had one brief glimpse of the outline of the volcano), but mile after mile of downed forest drove home the magnitude of the devastation.
I began bringing my students to the volcano in the 1990s once the road to the Johnston Ridge Observatory was opened. It provides an almost terrifying view into the maw of the gigantic crater, as well as a 360 degree view of the devastation. Tree trunks still litter the landscape, and only a few spindly conifers have begun to replace those that were blown away in 1980. The mountain ecosystem is well underway towards recovery however. Areas that were gray and dusty during my first visit are now green and covered by shrubs and wildflowers.
The mountain erupted again in 2004, and of course all the networks and cable new outlets converged on the mountain to report on the death and devastation. They hung around for a week or so and no one died, so they got bored and went back to their breathless coverage of missing white women (yes, that was a thing for months, and both stories involved Modesto in one way or another). The eruption continued for four more years, and a new 900 foot high dome appeared behind the 1986 dome.
The last time we tried to explore St. Helens with students was in 2011. The day was rainy and fog-bound, and we saw literally nothing of the volcano or the devastation, wasting hours of valuable time in the attempt. That was on my mind last June as we sized up the weather reports for the day of our expected visit... they called for rain. Mrs. Geotripper suggested we might skip a few "minor" stops the day prior to our scheduled visit, and catch the mountain in the late afternoon. It turned out to be a great idea, and all we missed was a view of the crater rim, due to the advance clouds from the coming storm.
The hummocky surface of the debris flow is still very evident in the valley of the Toutle River. The brush has had a harder time covering the small hillocks because soils can't readily develop on the steep slopes. Hundreds of new trees can be seen on the slopes beyond the valley floor however. Two new lakes formed in 1980 because the debris flow blocked some of the side canyons. Ecosystems are developing in these new environments as well.
The forest belt of Washington is not necessarily know for wildflower shows, but the slopes around the Johnston Ridge Observatory are for the time being vast meadows. Until the forest recovers, wildflowers will be part of the visitor experience.
As we traveled down the highway towards our camp, we noted a striking difference in the forest as we left the national monument and entered onto private lands owned by lumber companies. The forest was as uniform as a cornfield. The companies lost a great deal of timber during the eruptions, and it made sense to replant trees as quickly as possible. It's a bit disconcerting to see what amounts to monoculture going on. One hopes that these trees aren't vulnerable to the boring tree beetles that have destroyed forests across the western United States.
We headed down the hill to our camp at Seaquest State Park at Silver Lake. We had been privileged to see most of the volcano, and gained a perspective of the devastation from the ground. I wished I could have shown my students even more, and was reminded of a flight I took to Seattle a number of years ago. It happened to be one of those rare perfectly clear days, and the flight was only half full. The stewards gave me some dirty looks as I gleefully jumped from one side of the plane to the other snapping pictures of Cascades volcanoes (I got great shots of every volcano north of Crater Lake to Mt. Rainier). And I got pictures of Mt. St. Helens from the air for the first time.
We flew on the west side of Mt. St. Helens which provided me a view of Mt. Adams in the distance, and the Toutle River valley in the foreground. The gray strip of flood plain reveals the location of the debris avalanche, providing a perspective on the size of the flow.

In the big picture of Earth history, the eruption of Mt. St. Helens will barely register as a blip. Unless future researchers find the debris avalanche deposits, the record of the eruption in most places will be a thin layer of ash, at most a few inches thick. It would be an unremarkable eruption. But the eruption happened in modern times. We had accurate records of the volcano as it existed before, and excellent documentation of the events of May 18, 1980 (had the day been cloudy, we would be confused by some of the deposits). And we know what the volcano looks like today. The changes by any human standard were huge, and the effects on society very large. There was nothing small about the eruption of Mt. St. Helens.

If you are interested in the St. Helens story, may I recommend an excellent series on the eruptions by fellow geoblogger Dana Hunter at Rosetta Stones (click here for the index). She did a stellar job of bringing the volcano to life, along with the stories of those who were affected by the disaster.

Thursday, August 10, 2017

What Could be Worse than the Crater Lake Eruption? A look at Smith Rock State Park in Oregon

Standing on the rim of the Crater Lake caldera, as we did in our last post, it is hard to imagine the scale of the catastrophe. In that event just 7,700 years ago, 15 cubic miles of ash was blown into the atmosphere, covering much of western North America with volcanic dust. A similar-sized event at Tambora in 1815 caused the deaths directly of tens of thousands, and worldwide, possibly hundreds of thousands (from climate-induced famine). How could it be any worse? The answer is found not all that far away. On our Pacific Northwest journey last June, we stopped at Smith Rock State Park between the towns of Bend and Madras in Oregon. The two sites are about 120 miles apart.
Smith Rock State Park is small as such things go, only about a square mile, but the setting, as can be seen in these pictures, is rather spectacular. The 600 foot high tan-colored cliffs are popular with climbers, while a flat plateau (on the right side in the picture above) provides flatlands for parking and camping. The Crooked River flows through the park. How did these odd rocks come about?

The flat plateau is perhaps the easiest to explain. Newberry Crater is a massive basaltic shield volcano located about forty miles to the south. About 400,000 years ago, a basalt flow emanating from Newberry flowed north until it was stopped by the cliffs of Smith Rock. The Crooked River then eroded a channel between the contrasting rock types.

It is the tan cliffs that really tell the story of catastrophe. It was a disaster so huge that its dimensions were not recognized until fairly recent times. The cliffs of Smith Rock are part of the northwest corner of the Crooked River caldera, a sunken crater that is 25 miles long and 15 miles wide. Crater Lake's eruption produced around 15 cubic miles of ash. The Crooked River eruption produced around 200 cubic miles. Imagine a dozen Crater Lake eruptions happening at once and you start to get an idea. The eruption rivals some of the worst of the disasters at Yellowstone or Long Valley in eastern California. The only saving grace here is that the eruption took place around 29.5 million years ago. The magma chambers that fed the event have long since cooled.
As the hot ash landed, some parts remelted and cooled to form solid welded tuff. Other parts hardened as hot gases and steam coursed through gaps and openings called fumaroles. The cooling mass contracted and fractured into numerous joints. Differential erosion produced the various pinnacles and spires seen at the park.

Modern human beings have never experienced an eruption of this magnitude. The last one of this size worldwide, at Toba in Indonesia about 75,000 years ago, may have almost done in the human race (a controversial idea, but plausible). It involved around 470 cubic miles of ash.

I notice that Smith Rock sits at the south edge of totality during the coming Solar eclipse. If you are lucky enough to get to the park as a setting for this once in a lifetime event, I hope you'll spend a bit of time pondering the incredible history of these rocks as well.

For some detailed information about the history of the Crooked River Caldera, check this link.

Saturday, August 5, 2017

When Life Gives You a Single Point of View, Milk it For All it's Worth: Crater Lake in June

It never fails. I secretly control the incidences of drought and flooding in the western United States. How? By scheduling our summer field studies a full year in advance. The proof? Every time I schedule a Southwest trip, the climate changes to long-term drought, and it is a hot summer. Every time I schedule a trip to the Pacific Northwest, the drought breaks and we have record snowfall in the winter that doesn't melt until well into the summer. This was the case in 2011, our last northwest trip, and it was the case again this summer, in 2017.
In 2011, we saw that Crater Lake was snowbound, so we didn't even try to go there, heading into Newberry Crater instead. Even though somewhat lower, it was buried in snowdrifts as well. It had now been more than a decade since I had laid eyes on Crater Lake, so I planned the visit anyway, even though most of the roads were closed, and we would have to backtrack 80 miles off our trip route.
The only problem with having a single point of access and only a few parking lots plowed of snow was that only so many people could be accommodated in the park at a time, and June's massive heat wave was just getting started. People wanted to cool off, so they headed up into the mountains to Crater Lake. As a result spent 45 minutes in line at the entrance station, and our four vans were on their own for parking. We radioed each other to meet up at a rendezvous point near the rim once parking site was secured. So it was that instead of exploring a national park, we had the singular opportunity to view it from just one part of the rim.
And yet, what a sight it was! Just the dimensions are stunning. The lake is six miles across and 1,949 feet deep (542 meters), the deepest in the United States, the second deepest in North America, and the ninth deepest in the world (Baikal in Russia is the winner of that race, at 5,387 feet, or 1,642 meters). The deep blue color of the lake follows from the clarity of the water, which has been measured as deep as 175 feet (53 meters). It's not just the reflection of the sky above (note that the sky is lighter than the lake surface). The clear water absorbs the longer light waves at the red end of the spectrum, but scatters and reflects the shorter waves at the blue end of the spectrum.

The "crater" of Crater Lake is not a crater in the usual sense. It is a world-class example of a caldera, a volcanic feature that develops when a huge volume of ash explodes out of volcano, and the summit sinks into the void left behind. It was an unimaginable catastrophe. In the space of a few hours or days around 15 cubic miles of ash and debris were blasted into the atmosphere from the summit area of Mt. Mazama, the name given to the former volcano that became Crater Lake. What had once been a volcano as tall as 12,000 feet was now a smoking ruin with a rim barely exceeding 8,000 feet. The bottom of the caldera was another 4,000 feet lower. The ash was spread across the western United States and Canada, providing a crucial dating horizon for archaeologists (the ash has a unique chemical composition that can be identified in dig sites).
The lake itself, of course, came later. It is estimated that it took around 700 years for the lake to fill the depression to the level of the current day. There is no inlet or outlet. Water comes from snow and rain, and the level is balanced by evaporation and seepage (there are numerous springs around the flanks of the volcano). Fish are not native to the lake, but several kinds were introduced over the years. They don't do particularly well because of the purity of the water (there are few nutrients to support a food chain).

The Crater Lake caldera is young in the geologic sense, having erupted 7,700 years ago (+/- 150 years). Think about that: the ancestors of the indigenous people of the region saw and experienced this event. Their oral histories of the Klamath people recall the event. How many cultures in in today's world have collective memories that date back that far?
One might wonder if any eruptions from recorded history can match the violence of the Mazama eruption 7,700 years ago. It turns out there is. In 1815, Tambora, a 14,000 foot high volcano on the island of Sumbawa in Indonesia exploded with a fury equivalent to that of Crater Lake. The summit collapsed into a caldera in the manner of Crater Lake. After 200 years, a lake has begun to accumulate on the caldera floor.

Tens of thousands of people on the island died from the eruption itself or starvation later (all vegetation on the island was destroyed). So much ash was blown into the atmosphere that the climate cooled to the extent that snow fell during the summer months over much of the northern hemisphere. Famine contributed to hundreds of thousands of deaths around the world.
When we visited the park, the lake was still covered by snow, and crowded with tourists, but none of that could obscure the incredible story told by the rocks and water. The Cascade volcanoes are capable of great violence. The eruption of Mt. St. Helens in 1980 killed around four dozen people and did a billion dollars in damage, but the volume of that eruption was only about 1/60th the size of the eruption of Mazama 7,700 years ago. It's hard to imagine the effects of such an eruption in today's technological society. Would we be talking about it 8,000 years later?

Thursday, August 3, 2017

Dealing with the Dangerous Rays of Death: Singular Solar Events I've Seen

Do you ever look at the sun?

Some advice: DON'T LOOK AT THE SUN! You can destroy your eyes!

Good, now that we have that out of the way, what is this post all about? The sun has been on my mind the last few days. I'm preparing for the final adventure of the summer, and it has a lot to do with the sun, most specifically, the only eclipse to cross the lower 48 states since 1979, the first to cross the country in 99 years, and the last to cross the American West until 2045. I got to thinking about the singular events that I've seen over the years that involve the sun in some way or another.

The sun. A diameter of about 860,000 miles, more than 100 times the diameter of the Earth. About 93,000,000 miles away from Earth. Big enough to hold 330,000 Earths. Containing 99.86% of the mass of the Solar System. The source of energy that makes life possible on Earth.

The most obvious moments that we might pay attention to the sun are during sunrise and sunset. Every one is different and unique. At those times, the sun is at eye level, and the thickness (and dirtiness) of the atmosphere provide a bit of protection for viewing with the unprotected eye. As the sun passes across the horizon, light is split into bright colors of the spectrum, providing a beautiful spectacle. I've probably taken thousands of sunset and sunrise pictures over the years, but here are two of my favorites, a sunset in Newport California a few years ago (above), and sunrise over Lake Rotorua in New Zealand in 2004 (below). To this day I cannot keep straight my internal compass; I couldn't help but think the sun was rising in the west (it wasn't). Lake Rotorua is one of the world's rare geothermal regions with geysers. Hot springs in the lake account for the steam rising off the water.

A difficult phenomena to see related to sunsets is the green flash. It is a sudden flash of greenish light above the sun at the moment of sunset, and it is said to last only a second or so. As the sun dips into the horizon, the layers of the atmosphere will cause some of the sunlight to be refracted, with red and orange on the lower parts of the disk along with green (and rarely blue) across the top.
It takes some very specific circumstances to see the flash, a clear view to a distant horizon, most often along coastlines. I have relatives on the coast of Oregon, so I've had a fair number of chances to try and capture the moment. I may even have succeeded once or twice.
Rainbows are one of the most familiar optical effects associated with the sun. Most everyone has seen them, so it takes some unique circumstances to really set one apart from others. My favorite moment came with a monsoonal storm on the North Rim of the Grand Canyon last year. I was looking down at a rainbow in the depths of the canyon.
Rainbows involve the splitting of white light from the sun into its component colors of the spectrum. Caves and deep slot canyons provide another sort of splitting, that of the sun's energy into a more or less pinhole of light. I was exploring a lava tube in the Mojave National Preserve a few years back. It was dark inside, but there were a few small skylights, and the early afternoon sun came bursting through like a blast from alien phaser.
One of the more famous places to see beams of light from the sun is in Antelope Canyon, Arizona. A deep slot canyon, Antelope is one of the most popular tourist stops on the Navajo Nation. The sandstone canyon is more than 100 feet deep, and only a few feet wide at the top. One can actually jump across if it were allowed. Tours are offered all day, but one pays a premium around noon for the obvious reason that it's when the sun sends beams of light into the depths of the canyon.
The effect is truly spectacular, although one should be aware that as lonely as these pictures seem, I was shoulder to shoulder with other photographers snapping like crazy.

Another fascinating phenomena occurs when the Moon passes into the Earth's shadow, a lunar eclipse. They are not rare, happening around two times a year, and they can be seen simultaneously across the globe (as long as the moon is visible in the sky). 
Lunar eclipses are fascinating to watch, and it is surprising to realize just how much of the sun's light is reflected from the moon. At totality, the moon practically disappears except for some refracted light around the edge of the Earth. Hundreds of stars become visible that weren't there moments earlier.

In a ridiculous age when science has to convince some people that the Earth is not actually flat, a lunar eclipse can help. The Earth casts a circular shadow across the surface of the Moon.
And then there is the opposite number, those events that result from the Moon passing in front of the Sun, a Solar eclipse. Although the Sun is many times larger than the Moon, the Moon is much closer to the earth, and is thus big enough to blot out the sun entirely. Solar eclipses are rarer than Lunar eclipses, and total solar eclipses are rarer still. I've been able to photograph a number of partial Solar eclipses over the years. For me, it is a clumsy affair, trying to hold a filter over the lens while keeping the Sun in the frame, but I've surrendered to the use of a tripod a few times to make it work.

The picture above is one of my favorites because of the huge sunspots that were present during the Moon's transit across the disc of the Sun. If the eclipse occurs when the Moon is farther from the Earth (it has an elliptical orbit), an annular eclipse can occur, in which the Moon doesn't cover the entire disc of the sun. I caught the picture below in 2012.
And then there are the transits of the planets. These happen when a planet crosses the disk of the Sun. Only two planets can do this, Mercury and Venus, because they are the only planets with orbits that are closer to the Sun than Earth. I've witnessed two of them.
A transit of the planet Mercury took place in May of 2016. I almost missed it because of cloud cover, but they cleared enough for a couple of shots. There was a sunspot as well. In the picture below, the top arrow points to a sunspot. The lower arrow points to Mercury. It is a small planet, only barely bigger than the Moon, and it orbits much closer to the Sun. Such transits are only visible by binocular or telescope (with filters, of course).
Zooming in made Mercury a bit clearer (below). Transits of Mercury are not overly rare, occurring in 1999, 2003, 2006, and 2016. Another will take place in November of 2019, but then we will need to wait until 2032 to see another.
The rarest Sun-related event I've ever seen is a transit of the planet Venus. The one I witnessed happened in 2012 (below). Previous transits had been in 1874, 1882, and 2004. The next will not happen until 2117 (in December, if you are planning on watching).

The big event of all things Solar is of course a total Solar eclipse. As noted above, it's been decades since one took place in the lower 48 states, and next won't cross my neck of the woods until 2045. I'll be almost 90 years old if I make it that far. I've had the privilege of witnessing one, though, in 1991. It crossed the south end of Baja California at San Jose del Cabo. A small expedition from MJC drove the length of the Baja Peninsula to see the event, one of the great adventures of my life. I didn't get pictures at the time, as the best technology I had was a Kodak Instamatic. The pictures below are from Dr. William Luebke, MJC's retired astronomy professor.
There is nothing quite like the few moments of totality. The sky goes dark, stars and planets become visible, and the ambient temperature plummets (it was summer when we were there, and the temperature dropped from over 100 degrees to 80 or less; it was a relief). The corona of the sun becomes visible, and there may be solar prominences visible as well. We had more than four minutes of totality, more than usual.

It's going to be a zoo in Oregon in a few weeks, as literally millions of people are converging on the region to have a look at this rare event. We will be staying about an hour's drive from the path of totality, so I have no idea if we'll be able to even get to the dark zone through the gridlocked traffic. If we do, I'll be busy getting pictures to share, and if we don't...well...we'll always have Baja.