geologictimepics

Geology and Geologic Time through Photographs

Archive for the category “aerial photography”

Landscape and Rock–4 favorite photos from 2015

Landscape and bedrock… seems we seldom connect the two. We all like beautiful landscapes, but most of us don’t ask how they formed –and even fewer of us think about the story told by the rocks that lie beneath it all. Those make two time scales, the faster one of landscape evolution and the much slower one of the rock record. Considering that we live in our present-day human time scale, it’s no wonder there’s a disconnect!

Take this photo of Mt. Shuksan in northern Washington. My daughter Meg and I drove up to the parking lot at Heather Meadows and went for a quick hike to stretch our legs and take some pictures just before sunset.We had about a half hour before the light faded –and all I could think about was taking a photo of this amazing mountain. But the geology? What??

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1. Mt. Shuksan and moonrise, northern Washington Cascades.

Thankfully, I’d been there in September scoping out a possible field project with a new grad student, and had the time to reflect… on time. From the ridge we hiked, shown as the dark area in the lower left corner of the left-hand photo below, we could almost feel Shuksan’s glaciers sculpting the mountain into its present shape. Certainly, that process is imperceptibly slow by human standards.

Shuksan combo

Mt. Shuksan: its glaciated NW side, summit, and outcrop of the Bell Pass Melange.

But the glaciers are sculpting bedrock –and that bedrock reveals its own story, grounded in a much longer time scale.

It turns out that the rock of Mt. Shuksan formed over tens of millions of years on three separate fragments of Earth’s lithosphere, called terranes. These terranes came together along faults that were then accreted to North America sometime during the Cretaceous. At the top of the peak you can find rock of the Easton Terrane. The Easton Terrane contains blueschist, a metamorphic rock that forms under conditions of high pressures and relatively low temperatures, such as deep in a subduction zone. Below that lies the Bell Pass Melange (right photo) –unmetamorphosed rock that is wonderfully messed up. And below that lies volcanic and sedimentary rock of the Chilliwack Group.

Here’s another of my favorites from 2015: the Keystone Thrust! It’s an easy picture to take –you just need to fly into the Las Vegas airport from the north or south, and you fly right over it. It’s the contact between the gray ledgey (ledgy? ledgeee?) rock on the left and the tan cliffs that go up the middle of the photo.

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2. Keystone Thrust fault, Nevada–gray Cambrian ridges over tan Jurassic cliffs.

The gray rock is part of the Cambrian Bonanza King Formation, which is mostly limestone, and the tan cliffs consist of  Jurassic Aztec Sandstone. Cambrian, being the time period from about 540-485 million years, is a lot older than the Jurassic, which spanned the time 200-145 million years ago. Older rock over younger rock like that requires a thrust fault.

Talk about geologic history… the thrust fault formed during a period of mountain building during the Cretaceous Period, some 100-70 million years ago, long before the present mountains. And the rocks? The limestone formed in a shallow marine environment and the sandstone in a sand “sea” of the same scale as today’s Sahara Desert. We know it was that large because the Aztec Sandstone is the same rock as the Navajo Sandstone in Zion and Arches national parks.

Cambrian-Jurassic

left: Limestone of the Cambrian Bonanza King Formation near Death Valley; right: Cross-bedded sandstone of the Jurassic Navajo Sandstone in Zion NP, Utah.

So… the photo shows cliffs and ledges made of rocks that tell a story of different landscapes that spans 100s of millions of years. But today’s cliffs and ledges are young, having formed by erosion of the much older rock.  Then I flew over it in about 30 seconds.

At Beach 2 near Shi Shi Beach in Washington State are some incredible sea stacks, left standing (temporarily) as the sea erodes the headlands. The sea stack and arch in the photo below illustrates the continuous nature of this erosion. Once the arch fails, the seaward side of the headland will be isolated as another sea stack, larger, but really no different than the sea stack to its left. And so it goes.

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3. Sea arch and headland at Beach 2, Olympic Coast, Washington.

And of course, the headland’s made of rock that tells its own story –of  deposition offshore and getting scrunched up while getting added to the edge of the continent.

ShiShi

Bedrock at Beach 2 consists mostly of sandstone and breccia. The white fragment is limestone mixed with sandstone fragments.

And finally, my last “favorite”. It’s of an unnamed glacial valley in SE Alaska. My daughter and I flew by it in a small plane en route to Haines, Alaska to visit my cousin and his wife. More amazing landscape–carved by glaciers a long time ago. But as you can expect, the rock that makes it up is even older and tells it’s own story.

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4. Glacial Valley cutting into Chilkat Mountains, SE Alaska.

Of course, this message of three time scales, the human, the landscape, and the rock-record time scale applies everywhere we go. Ironically, we’re usually in a hurry. I wish I kept it in mind more often, as it might slow me down a little.

Here’s to 2015 –and to 2016.

To see or download these four images at higher resolutions, please visit my webpage: favorite 10 geology photos of 2015.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Aerial photos: Yellowstone Lake to Portland, Oregon at 30,000 feet

What a start to the new year!  January 1, I flew home to Oregon with a north-facing window seat on a spectacularly clear day.  So much incredible landscape!  So much incredible geology!  Here are nine photos I shot out the plane window, keyed to the geologic map below.

Yel-PDX + US map

Photo 1.  Absaroka Range, northern Wyoming and southern Montana.  You can see that these mountains consist of layered rocks (see bottom of photo especially)–but they’re not sedimentary.  They are basaltic to dacitic lava flows and pyroclastic rocks of the Absaroka Volcanic Field,  erupted from about 53-43 million years ago.  Much of the present topography is the result of glacial erosion during the Pleistocene.

Absaroka Range, east edge of Yellowstone Lake on left.

Absaroka Range, east edge of Yellowstone Lake on left.

 

Photo 2.  Yellowstone Lake.  As you can see on the map, Yellowstone Lake fills only a fraction of the caldera created by Yellowstone’s Lava Creek Eruption, 600,000 years ago.  Since then, rhyolite lavas, shown in pink, filled in the caldera.  Notice the oval-shaped bay at the end of the lake’s western arm.  It’s called West Thumb, and is a younger caldera that erupted about 150,000 years ago.  It’s a caldera within a caldera!  It’s pretty big too– almost identical in size to Crater Lake in Oregon –but compared to the main caldera, it’s tiny.

Photo and geologic map of Yellowstone National Park

Photo and geologic map of Yellowstone National Park. The dashed red line marks the caldera edge.

 

Photo 3. Recent faulting of the Basin and Range Province. In this photo, the Pahsimeroi River flows northwestward to its confluence with the Salmon River, near the left side of the photo –and the Salmon continues flowing northward for about 100 miles before it turns westward and eventually joins the Snake River.

Recent faulting along western edge of Lemhi Range, Idaho.

Recent faulting along eastern edge of Pahsimeroi Valley, Idaho–and western front of Lemhi Range.

But what I think is so cool about this photo is that it so clearly shows the abrupt western edge of the Lemhi Range, which runs diagonally from the right (east) side of the photo to just above the center.  The range literally rises right out of the ground.  That abruptness is caused by faulting that takes place recently and frequently enough that erosion doesn’t keep up with it.  The fault is a normal fault, caused by crustal extension.  Notice the linear nature of the ranges to the northeast (upper right) –More normal faulting!  This is a northern expression of the Basin and Range Province.  Woohoo!

 

Photo 4. Mountains of the Idaho Batholith.  Granitic rock of the Idaho Batholith underlies a huge area of Idaho, some 14,000 square miles of it. On the geologic map, it’s the big green area.  The rock intruded as a series of plutons during the Late Cretaceous, from about 100 – 65 million years ago.  Similar in age and composition to the Sierra Nevada Batholith, the Idaho Batholith was fed by magma created during subduction along the west coast of North America.

Mountains of the Idaho Batholith

Mountains of the Idaho Batholith

 

Photo 5. Hell’s Canyon.  Not only does the north-flowing Snake River in Hell’s Canyon form the boundary between Idaho and Oregon (Yay, we made it to Oregon!), and not only is it the deepest canyon in the conterminous United States, but it’s also incredibly important from a geologic-history-of-western-North-America point-of-view.

Notice the flat areas above the canyon–they’re especially visible on the west (left) side, but you can also see them on the east.  Those places are flat because they’re made of flat-lying basalt of the Columbia River Basalt Group. These basalts erupted mostly between 17-14.5 million years ago, but kept erupting off and on until about 6 million years ago –and they cover ALL of northern Oregon and ALL of southeastern Washington State.  In fact, they flowed all the way to the Pacific Ocean.

Hell's Canyon and the Snake River.

Hell’s Canyon and the Snake River. The Imnaha River forms the next deep canyon to the left (west).

Those basalt flows overlie rock of the Wallowa accreted terrane: mostly volcanic and sedimentary rock that formed in an island arc setting, far offshore from North America.  It was added (accreted) to the North American continent during the Mesozoic –probably some 150 million years ago.

 

Photo 6. Wallowa Mountains, Oregon. Just west of Hell’s Canyon are the Wallowa Mountains, Oregon’s premier alpine country outside of the Cascades.  Like Hell’s Canyon, the Wallowas contain the accreted Wallowa terrane overlain by Columbia River Basalt –but the Wallowas also host the Wallowa Batholith, a Jurassic-Cretaceous granitic “stitching pluton”.  It’s called a stitching pluton because it intrudes across accreted terranes and “stitched” them together.

Glacial valleys and frontal fault zone on the north side of the Wallowa Mountains, Oregon.

Glacial valleys and frontal fault zone on the north side of the Wallowa Mountains, Oregon.

You can see a bunch of other things in this photo though.  First off, the mountains end suddenly in a line: a recently active fault zone that has uplifted them more than 5000′ relative to the valley floor. Also, you can see how glaciers carved the landscape.  Notice the deep U-shaped valleys, cirques, and knife-edged ridges called aretes.  And see the lake in the upper right corner of the photo?  It’s Wallowa Lake, dammed by a glacial moraine!

(at this point, the folks in the seats next to me wanted to throw me out of the airplane)

 

Photo 7. View of Washington High Cascades over The Dalles.  That’s Mt. St. Helens on the left (west), Mt. Adams in the middle, and Mt. Rainier in the far distant right.  Mt. Rainier is 90 miles away!

Looking north over the Dalles to Mts. St Helens, Rainier, and Adams.

Looking north over the Dalles to Mts. St Helens, Rainier, and Adams.

These volcanoes are dormant –which means that they’re …sleeping?  And they can awaken at any time.  I remember a college friend of mine wanted to climb Mt. St. Helens in 1979.  It was dormant then, and nobody worried about it.  Then in May, 1980 it erupted violently, blowing off its top 2000′.  Both St. Helens and Mt. Rainier have erupted many times in the past several thousand years; Mt. Adams though, erupted only twice in that period.

 

Photo 8.  Columbia Gorge, the Washington High Cascades, and the Bonneville Landslide.  From left (west) to right, the volcanoes are Mt. St. Helens, Mt. Rainier, and Mt. Adams.  You can see the Bonneville Landslide along the river on the right side of the photo, directly below the left base of Mt. Adams.  It detached from the cliffs directly behind it about 1450 A.D. and slid right into the river –and it pushed the river about a mile to the south! Just downriver from the landslide, you can seevthe Cascade Locks zig-zagging across the river.

View northward over the Columbia River Gorge to the Washington High Cascades.

View northward over the Columbia River Gorge to the Washington High Cascades.

The ridges at the bottom of the photo lead up to Mt. Hood, another dormant stratovolcano and Oregon’s highest peak.  Apparently, the view out the south side of the plane was even more ridiculously cool.

 

Photo 9. Columbia River, just below Portland.  Right near Portland, the Columbia River turns northward for about 40 miles before it heads west again out towards the Pacific–and it drops only 10 feet in elevation for the whole distance.  The northward deflection of the river is probably the result of uplift of the Portland Hills, which likely began as long as 16 million years ago (they also deflect 16 million year old lava flows of the Columbia River Basalt). That town along the river in the background is St. Helens, Oregon.

View northward, down the Columbia River.

View northward, down the Columbia River, Washington on the right, Oregon on the left.


See more geologic photos of Oregon by typing “Oregon” into the geology search engine on my website –or type “Oregon, aerial” if you want to see aerial shots!  And if you’re suddenly really excited about Oregon geology, please check out the new edition of Roadside Geology of Oregon!

 

 

 

Geologic Irony in Cincinnati and northern Kentucky! Deep geologic time everywhere –and the absurd denial of the Creation Museum.

It’s been awhile since I’ve posted –too many things have been happening, like the end of fall term, other deadlines, and of course, coming down with a bad cold!  But I did manage to visit Cincinnati, Ohio for Thanksgiving.  I’m originally from Cincinnati, and I always enjoy going back.

Ordovician shale and limestone along I-75 in northern Kentucky; downtown Cincinnati, Ohio occupies the background

Ordovician shale and limestone along I-75 in northern Kentucky; downtown Cincinnati, Ohio occupies the background

Besides visiting with old friends, one thing I love about the Cincinnati-Northern Kentucky area, is the incredible wealth of marine fossils in its rocks, which date from the Ordovician Period, some 475 million years ago.  It’s always amazing to me that I can, almost at random, pick up a rock and see the remains of critters that were actually alive so long ago.  It fills me with a sense of wonder, mystery, and awe that I’ll never be able to explain –and it demonstrates to me how I’m a part of the earth –not apart from it.

marine fossils in Ordovician limestone from northern Kentucky --you can see mostly brachipods (they look sort of like clam shells) and bryozoa (branching coral-like things) in this rock.

marine fossils in Ordovician limestone from northern Kentucky –you can see mostly brachipods (they look sort of like clam shells) and bryozoa (branching coral-like things) in this rock.

Really, these fossil-rich limestones are just about EVERYWHERE!  Even many of the stone buildings and walls that you can see throughout Cincinnati, are full of Ordovician marine fossils.

And what a wonderful setting!  The Ohio river cuts through its original floodplain, now perched a couple hundred feet above the river.  That’s actually a whole story in itself, because today’s Ohio River formed as a result of the continental ice sheet advancing across northern Ohio, and blocking the courses of several north-flowing rivers, such as the Kentucky and Licking Rivers.

Looking up the Ohio River from the air --near where Ohio, Kentucky, and Indiana meet.

Looking up the Ohio River from the air –near where Ohio, Kentucky, and Indiana meet.

And then there’s the Creation Museum in northern Kentucky, perched on the old river terrace above bedrock of fossil-rich Ordovician limestone and shale.  One look at the two photos below and you can see what they’re all about.

The explanation for fossils according to the Creation Museum (on the left), and a diorama depicting a human being coexisting with a dinosaur on the right.

The explanation for fossils according to the Creation Museum (on the left), and a diorama (on the right) depicting a human being coexisting with a dinosaur.

According to “The Museum”, fossils “were formed by Noah’s Flood (~4,350 years ago) and its aftermath” –and dinosaurs really did coexist with humans.  In fact, I read that before Adam and Eve ate their apple, T Rex dinosaurs were actually vegetarian.

But don’t take it from me that those limestones are actually very old (100s of millions of years, as opposed to 4,350 years).  Take a look at a geologic map.  The Cincinnati-Northern Kentucky area is underlain by more than 1000 feet of limestone and shale –and if you travel eastward or westward, you encounter 1000’s more feet of marine sedimentary rock that sit on top the Ordovician.  And the fossils in those rocks show a change with time, called evolution.  If you think about it, you’re looking at a long long time to deposit –and preserve–all that sediment.

Geologic map of the United States; the area around Cincinnati is enlarged.  "CM" shows the approximate location of the Creation Museum.

Geologic map of the United States; the area around Cincinnati is enlarged. “CM” shows the approximate location of the Creation Museum.

The Creation Museum tells us that all that sediment was deposited by “the flood”.  Never mind that very little of the rock contains particles even as big as a sand grain.  Below is a photo of a real flood deposit.  As you can see, the deposit is very coarse-grained!  It’s coarse-grained because large floods are very energetic and transport large particles.

Coarse-grained sediment, deposited by one of the Missoula Floods in Oregon, some 15,000 years ago.

Coarse-grained sediment, deposited by one of the Missoula Floods in Oregon, some 15,000 years ago. The exposure is about 20 feet high.

So the Creation Museum is asking you to BELIEVE that 1000s of feet of limestone were deposited by a flood, as well as the 1000s of feet of older rocks and 1000s of feet of younger rocks I didn’t even mention.  They also want you to believe that T. Rex was a vegetarian who lived alongside Adam and Eve.

But here’s what really bothers me: by misrepresenting science and promoting its own skewed interpretation of the bible as the literal Truth, the “museum” discourages people from looking at these beautiful rocks with a sense of wonder, mystery, and awe.  It discourages them from inquiring into how those rocks really formed.  The museum discourages people from learning important things about our planet and from forming their own views on the world.

Me petting a dinosaur at the Creation Museum

Me petting a dinosaur at the Creation Museum.


Type “Ordovician” into the search for a few more photos of Ordovician fossils.

California’s largest lake formed by its largest fault zone: the Salton Sea and San Andreas Fault

With a surface area of nearly 1000 square kilometers (381 square miles), the Salton Sea is California’s largest lake.  But it’s relatively shallow –and because it has no outlet, it’s saltier than ocean water.  It formed in 1905 when the nearby Colorado River overwhelmed irrigation canals and flooded the region.  Now it’s an incredibly important migratory bird refuge, fishery, and dumping ground for agricultural waste.  Seems like those things shouldn’t really go together!

Aerial view of the Salton Sea, looking northward.

Aerial view of the Salton Sea, looking northward.

But it just seems young.  The Salton Sea actually occupies part of the Colorado River Delta –and as a result, has been filled with freshwater multiple times since the delta was first constructed, probably near the beginning of the Pleistocene.  It’s also at the remarkably low elevation of 234 feet (71m) below sea level; the deepest part of the lake is 44 feet (13 m) below that.

And the low spot is there because of extension caused by the San Andreas fault system!  The San Andreas fault terminates along the eastern margin of the lake basin, but steps across the lake to the Imperial fault, which forms its western margin.  Both faults are right-lateral –and because they step to the right, they pull the area apart in-between them.  Kind of like central Death Valley –which is even lower in elevation than the Salton Sea!  But more on Death Valley later.

Aerial view of Salton Sea, with the approximate locations of the southern San Andreas and Imperial faults.  Note how right-lateral slip on the two en-echelon faults drive extension between them.

Aerial view of Salton Sea, with the approximate locations of the southern San Andreas and Imperial faults. Note how right-lateral slip on the two en-echelon faults drive extension between them.


click here to see more photos of the San Andreas fault system, or click here to see a photo geology tour of Death Valley, California.

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