geologictimepics

Geology and Geologic Time through Photographs

Iceland –where you can walk a mid-Atlantic rift –and some other geology photos

While Iceland hosts an amazing variety of awesome landscapes, what stands out to me most are its incredible exposures of the Mid-Atlantic ridge. To the north and south, the ridge lies beneath some 2500m of water, forming a rift that separates the North American plate from the Eurasian plate. The rift spreads apart at a rate of some 2.5 cm/year, forming new oceanic lithosphere in the process. But in Iceland, you can actually walk around in it!

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Geologic map of Iceland as compiled from references listed below.

If you look at the geologic map above, you can see two rift zones near Iceland’s mid-section, and that the rocks become older in either direction away from those zones –just what you’d expect. New material erupts in the rift zones as they pull apart, separating the two major tectonic plates. In Iceland there’s a third microplate between the two rifts. The process continues through time, creating volcanic activity with ages somewhat symmetrical about each of the rifts. From the map, you can also see that most of Iceland’s big thermal areas lie within the rift zones.

Geothermal power plant, Iceland

Geothermal power plant in the Western Rift Zone, just east of Reykjavik

It’s more complicated though. A hot spot beneath Iceland causes increased volcanic activity, which through time, thickened the Icelandic crust to greater than 40 km in places. By comparison, most of the oceanic crust beneath the North Atlantic ranges from 4-7 km thick. Icelandic magma, rising from its source in the underlying mantle, must therefore pass through a lot more rock, which gives it plenty of time and opportunity to evolve into more silicic varieties. If you look at the geologic map’s legend, you can see that besides basalt (which is the rock of the ocean floor), you also see a lot of andesite and even some rhyolite. In fact, Iceland contains numerous stratovolcanoes, several of which have erupted silicic ash and pumice in the last couple thousand years, including Hekla and Snaeffelsjökull, shown on the map.

Snæfellsjökull volcano and glacier, Iceland

Snæfellsjökull volcano and glacier. There’s a moss-covered basalt flow in the lower part of the photo; the upper reaches of the volcano are more silicic.

What I found so instructive was the physical layout of the rift zones. There’s not a single, discrete crack that marks where all the lava comes up. Each zone is at least several km in width –and marked by numerous discontinuous fissure zones, active at different times than each other. Near Reykjavik, these features are beautifully expressed—and accessible—at Thingvellir National Park as well as along the south coast of the Reykjanes Peninsula.

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Western Rift Zone at Thingvellir, view northward. Besides the prominent fissures on the left (west), numerous other ones cut the interior of the rift, 3 of which are marked by arrows. The rift continues up the valley behind the arrows.

And the lava flows –they too erupt at different times and different places –and not always from an existing fissure. Sinton and others (2005), for example, map more than 30 different post-glacial flows at various places within the western rift zone. Most of the recent activity, however, lies within the eastern rift zone. Since the year 2000, some six separate eruptions occurred within or at the margins of the eastern rift zone. These eruptions include the 2010 eruption of Eyjafjallajökull, which took place beneath a glacier. The water-magma reactions created a gigantic ash cloud that disrupted European air traffic for nearly a week –my oldest daughter got stranded in Ireland!

Eyjafjallajokull Volcano as seen from Heimaey

Eyjafjallajokull Volcano as seen from island of Heimaey

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Through time, the Mid-Atlantic ridge has split N and S America from Europe and Africa  (USGS)

 

These observations are important because we tend to present rifting and its accompanying volcanism as a steady, continuous process. We ask students to imagine opposing conveyor belts moving outwards from a central area to help visualize the process. But more accurately, the conveyor belts are partially broken and rusty and so move in only fits and starts –and mostly, the conveyor belts seem stuck. If you walked through the rift zone on any typical day, you might perceive that the whole process had simply stopped. And that’s the point. At human time scales, this rifting process is inexorably slow, almost imperceptible. But through geologic time it creates the enormous changes we can see.

 

To make Iceland even more complex –and interesting—the Snaeffelsnes Peninsula, north of Reykjavik, marks an earlier position of the rift. The rift migrated some 6-7 million years ago to today’s western rift zone. The peninsula’s main volcano, the ice-capped Snaeffelsjökull stratovolcano is still potentially active, having last erupted sometime around 200 AD.

Holocene lava flow near Snaeffelsjokull

Holocene lava flow near Snæfellsjökull

 

So here’s a bit of a photo dump. I visited the SW third of Iceland during early September, 2018 with my friends Christine and Charlotte and shot nearly a zillion photos. What a landscape! While these are some of my favorite photos, I posted more than 100 others on my geology photo website and they’re all freely available to download. Just type “Iceland” into the search!

click on any photo (including the ones above) to see it larger and in a separate window

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Christine and Charlotte one evening

Gravel bar in braided river, Iceland.

One of my favorites, a gravel bar near the south coast

 

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We met up with a Geo group from Colorado College (where Christine teaches) -these are glacial deposits.

Columnar-jointed basalt, Iceland

The CC group took us to these basalt columns near Vik –columns in 3D!

Eldfell cinder cone and Heimaey, Iceland

Eldfell cinder cone and town on Heimaey. In 1973, the cinder cone erupted, destroying parts of the town and nearly blocking the harbor. Icelanders stopped the lava using seawater!

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Airfall deposits from earlier eruptions on Heimaey –with projectiles!

Rift valley within W Rift Zone, Iceland

One of the fissures in the W Rift Zone of Thingvellir NP.

Feeder dike intruding tephra (Vertical)

Christine and a feeder dike

Rocky coastline and breaking wave,  Iceland

Breaking wave on the S Coast

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and moss…

 

 


Some References:
Sinton, J., Gronvold, K., and Saemundsson, K., 2005, Postglacial eruptive history of the western Volcanic Zone, Iceland: Geochemistry, Geophysics, Geosystems, v. 6, no. 12.
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2005GC001021

Great general reference (thanks Tom!)  Gudmundsson, A.T., 2007, Living Earth, Outline of the Geology of Iceland, Mál og menning, Reykjavik, 408p.

References used for map:
Jóhannesson, H., 2014, Geological map of Iceland. Bedrock Geology, 1:600,000. Icelandi Institute of Natural History. http://en.ni.is/outreach-and-publications/publications/maps/geological-maps/600000.html

Geothermal sources of energy in Iceland. Water and Fire: https://waterfire.fas.is/GeothermalEnergy/SteamPower.php

Islam, Md. Tariqul, 2016, Rheological response to tectonic and volcanic deformation in Iceland, Thesis, University of Gottenburg, https://www.researchgate.net/publication/303549562_Rheological_response_to_tectonic_and_volcanic_deformation_in_Iceland

 

Hug Point State Park, Oregon, USA –sea cliffs expose a Miocene delta invaded by lava flows

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Alcove and tidepool at Hug Point

Imagine, some 15 million years ago, basaltic lava flows pouring down a river valley to the coast –and then somehow invading downwards into the sandy sediments of its delta. Today, you can see evidence for these events in the sea cliffs near Hug Point in Oregon. There, numerous basalt dikes and sills invade awesome sandstone exposures of the Astoria Formation, some of which exhibit highly contorted bedding, likely caused by the invading lava. It’s also really beautiful, with numerous alcoves and small sea caves to explore. And at low to medium-low tides, you can walk miles along the sandy beach!

(Click on any of the images to see them at a larger size)

Read more…

Devil’s Punchbowl –Awesome geology on a beautiful Oregon beach

You could teach a geology course at Devil’s Punchbowl, a state park just north of Newport, Oregon. Along this half-mile stretch of beach and rocky tidepools, you see tilted sedimentary rocks, normal faults, an angular unconformity beneath an uplifted marine terrace, invasive lava flows, and of course amazing erosional features typical of Oregon’s spectacular coastline. And every one of these features tells a story. You can click on any of the images below to see them at a larger size.

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View southward from Cape Foulweather to the Devil’s Punchbowl.

 

180629-58ceThe rocks. They’re mostly shallow marine sandstones of the Astoria Formation, deposited in the early part of the Miocene, between about 16.5 to 22 million years ago. The rocks are tilted so you can walk horizontally into younger ones, which tend to be finer grained and more thinly bedded than the rocks below. This change in grain size suggests a gradual deepening of the water level through time. In many places, you can find small deposits of broken clam shells, likely stirred up and scattered during storms –and on the southern edge of the first headland north of the Punchbowl, you can find some spectacular soft-sediment deformation, probably brought on by submarine slumping. Later rock alteration from circulating hot groundwater caused iron sulfide minerals to crystallize within some of the sandstone. Read more…

Grand Canyon Unconformities –and a Cambrian Island

A prominent ledge punctuates the landscape towards the bottom of the Grand Canyon. It’s the Tapeats Sandstone, deposited during the Cambrian Period about 520 million years ago, when the ocean was beginning to encroach on the North American continent, an event called the Cambrian Transgression. Above the ledge, you can see more than 3000 feet of near-horizontal sedimentary rocks, eroded into cliffs and slopes depending on their ability to withstand weathering and erosion. These rocks, deposited during the rest of the Paleozoic Era, are often used to demonstrate the vastness of geologic time–some 300 million years of it.

View of the Grand Canyon from the South Rim trail. Arrows point to the Cambrian Tapeats Sandstone.

View of the Grand Canyon from the South Rim trail. Arrows point to the Tapeats Sandstone.

But the razor-thin surface between the Tapeats and the underlying Proterozoic-age rock reflects the passage of far more geologic time  –about 600 million years where the Tapeats sits on top of the sedimentary rocks of the Grand Canyon Supergroup. Those rocks are easy to spot on the photo above because they contain the bright red rock called the Hakatai Shale. Even more time passed across the surface where the Tapeats sits on top of the 1.7 billion year old metamorphic basement rock. You can put your thumb on the basement and a finger on the Tapeats –and your hand will span 1.2 billion years! Read more…

Sampling New Zealand’s (Amazing) Geology

New Zealand’s landscape can make just about anybody appreciate geology. Its glaciated peaks, its coastline –that ranges from ragged cliffs to sandy beaches to glacial fjords– its active volcanoes… they all work together to shout “Earth Science!” With that in mind, here’s some basics of New Zealand’s amazing geology, followed by some geological highlights of my trip of January and early February, 2018.

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Map of New Zealand, showing accreted terranes in colors and cover assemblage in gray.

North and South Island Bedrock  The different colors on this map show New Zealand’s basement rock, named so because it forms the lowest known bedrock foundation of any given area. The basement tells stories of New Zealand’s deep past, from about 500-100 million years ago. Individual colors signify different terranes, accreted (added) one-by-one through plate motions to the edge of what was then the supercontinent Gondwana. They mostly consist of sedimentary and metamorphosed sedimentary rock, although the narrow belt of purple-colored Dun Mountain Ophiolite formed as oceanic lithosphere, and the red-colored areas consist of granitic igneous rock, some of which has been metamorphosed to gneiss.

Gray indicates the younger cover rock, formed after accretion of the terranes. Consisting of a wide range of sedimentary and volcanic rocks, as well as recently deposited sediment, it’s just as interesting and variable as the terranes. Because it includes volcanoes, it’s largely the cover that gives the North Island its distinctive flair. By contrast, the South Island consists largely of uplifted basement rock, much of which has been –and still is—glaciated. All those long deep lakes, such as Lakes Wanaka and Tekapo, were carved by glaciers and are now floored with their deposits of till.

Andesite stratovolcano, New Zealand

Mt. Ngauruhoe, a 7000 year-old andesite stratocone near Ruapehu on the North Island

Those differences exist largely because the North and South Islands occupy different plate tectonic settings. The North Island sits over a subduction zone, so it hosts an active Read more…

Cove Palisades, Oregon: a tidy short story in the vastness of time

If I were a water skier, I’d go to Lake Billy Chinook at Cove Palisades where I could ski and see amazing geology at the same time. On the other hand, I’d probably keep crashing because the geology is so dramatic! Maybe a canoe would be better.

Lake Billy Chinook, Oregon

View across the Crooked River Arm of Lake Billy Chinook to some of the 1.2 million year old canyon-filling basalt (right) and Deschutes Fm (left). The cliff on the far left of the photo is also part of the 1.2 million year basalt.

The lake itself fills canyons of the Crooked, Deschutes and Metolius Rivers. It backs up behind Round Butte Dam, which blocks the river channel just down from where the rivers merge. The rocks here tell a story of earlier river canyons that occupied the same places as today’s Crooked and Deschutes Rivers. These older canyons were filled by basaltic lava flows that now line some of the walls of today’s canyons.

CovePalisades2From the geologic map, modified from Bishop and Smith, 1990, you can see how the brown-colored canyon-filling basalt, (called the “Intracanyon Basalt”) forms narrow outcrops within today’s Crooked and Deschutes canyon areas. It erupted about 1.2 million years ago and flowed from a vent about 60 miles to the south. You can also see that most of the bedrock (in shades of green) consists of the Deschutes Formation, and that there are a lot of landslides along the canyon sides.

The cross-section at the bottom of the map shows the view along a west-to-east line. Multiple flows of the intracanyon basalt filled the canyon 1.2 million years ago –and since then the river has re-established its channel pretty much in the old canyon. While the map and cross-section views suggest the flows moved down narrow valleys or canyons, you can actually see the canyon edges, several of which are visible right from the road.

Read more…

Rocks! –a brief illustrated primer

click on any image to see a larger version

Seems like most people I know like rocks. They bring home unusual rocks from vacations; they admire beautiful facing stones on buildings; they frequently ask “What is this rock”? Considering that the type of rock you’re looking at reflects the processes that caused it to form, some basic rock identification skills can go a long way to understanding our planet!

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Rock (left, igneous-granite) and minerals (right, quartz and kyanite). Notice that the granite is made of a variety of minerals.

Of course there are thousands of different rock types —But! they ALL fit into one of three categories: igneous, sedimentary, or metamorphic. Here’s a brief, illustrated summary of each.

Igneous rocks are those that form by cooling and crystallization from a molten state. Consequently, they consist of crystals of various minerals that form an interlocking mosaic like the rock in the photo to the right. Igneous rocks are further classified as “intrusive” or “extrusive”, depending if they form beneath Earth’s surface (intrusive) or on Earth’s surface (extrusive). Extrusive rocks are more commonly called volcanic rocks. Generally speaking, intrusive rocks are coarsely crystalline whereas volcanic ones are finely crystalline. Check out this gallery of igneous rock photos.

Sedimentary rocks are made of particles (“sediment”) of pre-existing rock that are deposited as layers on Earth’s surface and then become cemented together. Individual layers of sedimentary rock are called “beds”. Bedding is best observed from a distance; most individual sedimentary rocks come from within a bed and so may appear homogeneous. Check out this gallery of sedimentary rock photos.

Metamorphic rocks are pre-existing rocks that change (“metamorphose”) because they are subject to high temperatures and/or pressures. This change involves the growth of new crystals in the rock. Because this growth typically occurs under conditions of high pressure as well as temperature, the new minerals tend to grow in a preferred orientation, leading to a fine-scale layering in the rock. This layering is called foliation. Unlike bedding in sedimentary rock, foliation tends to be irregular and marked by differently colored zones of different minerals. Check out this gallery of metamorphic rock photos.

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Sedimentary (sandstone, L), Igneous (granite, Ctr), and Metamorphic (gneiss, R) specimens

Key

simplified key to recognizing main rock types

Telling Igneous, Sedimentary, and Metamorphic rocks apart is usually pretty easy. First, decide if the rock consists of crystals or rounded grains. If it consists of crystals, then it is igneous or metamorphic; if it consists of grains, then it is sedimentary. If the crystals are arranged into layers or bands, the rock is metamorphic; if they are randomly arranged, then it is igneous. Igneous rocks with large crystals generally indicate slow cooling within the earth (intrusive). Conversely, igneous rocks with small crystals generally indicate rapid cooling on Earth’s surface (volcanic).

Igneous Rock –more details

Intrusive and volcanic rocks are further classified based on their chemistry and texture according to the chart below. This is one place where mineral identification becomes very important because minerals reflect the rock’s chemistry. Importantly, rocks with high silica content, such as rhyolite and granite, typically have fairly low iron contents, and so tend to have minerals that are light in color, such as K-feldspar, sodium-rich plagioclase, and quartz. Conversely, rocks with low silica content, such as basalt and gabbro, typically have high iron contents, and so have minerals that tend to be dark in color.

 Intro-1. Ig rx-CS4
Principal igneous rock types. Their classification depends on texture and composition. Fine-grained rocks are extrusive (upper row), whereas coarse-grained rocks are intrusive (lower row). Silica content then determines the specific rock name: gabbro and basalt <50-57%, SiO2; diorite and andesite, 57-67%; granite and rhyolite, 67+%.   Notice that rocks tend to be darker, denser, and more iron rich towards the lower silica end of the spectrum.

More on Volcanic Rock
Being igneous, volcanic rocks are made of crystals –but they’re so fine grained, you often can’t see that without a microscope. Thankfully, many volcanic rocks contain phenocrysts, larger crystals surrounded by the finer grained matrix. If you look closely at the photos of basalt and andesite above, you can see phenocrysts of plagioclase feldspar as the small white things.

Below are more photos, showing a more enlarged view of a rock with phenocrysts. Note how fine grained the surrounding matrix is –you can’t really see anything at all. If you look at the microscopic view though you can see that the whole rock is crystalline, even the super-fine matrix. The point here is that, unless the rock contains glass (see next section), the whole rock is crystalline!

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Porphyritic volcanic rock in hand sample (left) and microscopically (right). Note how microscopic view

Volcanic: Glass
One of the more ubiquitous volcanic products, volcanic glass is just that –glass–so it lacks a crystal structure. Glass can form when the lava is so dry as to inhibit crystal growth, as in obsidian, or when lava cools so quickly as to prevent crystal growth, such as with volcanic ash and pumice.

The photos below show pumice, which is frothy volcanic glass. It gets that texture because it forms during violent eruptions –explosively expanding gases in the lava shatter the fast-cooling material so that the rock consists of air bubbles (called vesicles) separated by glassy sidewalls.

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Pumice: frothy volcanic glass from instantaneous cooling. Left-hand image shows close-up view of glass threads. Paper clip for scale.

Volcanic: Pyroclastic Material and Rocks
Pyroclastic materials (also called “tephra”) form during explosive eruptions and so consist of rock fragments and glass ejected violently from the volcano. We classify it according to its size: large fragments are called blocks or bombs; small particles, between about 2mm – 64mm, are called “lapilli”; tiny particles, smaller than 2mm, are called “ash“.  Pumice is also pyroclastic, but it’s considered its own rock type –and it can be of any size. Pyroclastic falls can result from any explosive eruption in which pyroclastic materials fall out from the atmosphere; pyroclastic flows are those that flow out over the ground surface.

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Most tuff contains fragments of pumice in a matrix of ash

Now the rocks. The most common pyroclastic rock is undoubtedly “tuff”, which is composed largely of ash and pumice fragments, erupted mostly during rhyolitic eruptions. Air fall tuff forms from ash that accumulates in layers as it settles from the atmosphere; Ash flow tuff forms from bodies of ash that flow rapidly along the ground, typically incinerating everything in their paths. Because the material flows, it typically does not form layers. Many ash flow tuffs are welded (called “welded tuff”) because of the high temperatures. These highly welded tuffs are sometimes called “ignimbrites”. To identify tuff, look for pieces of pumice floating around in the ashy matrix.

Below’s a view of the Bandelier Tuff in northern New Mexico. It’s a series of ash flow tuffs formed during huge eruptions 1.6 and 1.25 million years ago in the Jemez Mountains. These eruptions formed the Valles-Toledo Caldera (generally just called the “Valles Caldera”). You can get an idea as to the size of the eruptions based on the size of the flows: they’re thick!

Bandelier Tuff, Los Alamos, New Mexico

Cliffs of Bandelier Tuff, erupted from Valles Caldera, New Mexico.

New Zealand’s Taupo Volcanic Zone hosts the most frequent recent rhyolitic eruptions than anywhere else in the world, all active in the last 2 million years. The most recent big eruptions, 26,500 and 1800 years ago, were centered on Lake Taupo, near the middle of the North Island. Below is a map showing the distribution of airfall and ignimbrite (welded ash flow) deposits formed during the eruption at AD 186, just over 1800 years ago. The estimated volume of all eruptive products during this eruption exceeds 105 km3 (Wilson, and Walker, 1985). By comparison, the older “Oruanui” eruption, 26,500 years ago? It likely erupted more than 1000 km3! (Wilson, 2001).

Taupo deposits

Taupo vent (red triangle) and distribution of airfall and ashflow deposits from AD186 eruption.  Inset shows Taupo Volcanic Zone on New Zealand’s North Island. From Wilson and Walker, 1985.

references for Taupo eruptions:
Wilson, C.J.N., and Walker, G.P.L., 1985, The Taupo eruption, New Zealand i. General Aspects, Philosophical Transactions of the Royal Society of London, v. 314, p. 199-228.

Wilson, C.J.N., 2001, The 26.5 Oruanui eruption, New Zealand: an introduction and overview, Journal of Volcanology and Geothermal Research, v. 112, p. 133-174).

Sedimentary Rock –More details

Sedimentary rock may be clastic, biogenic, or chemical, depending on how the particles formed. Clastic sedimentary rocks contain actual pieces of the pre-existing rock that have been transported from the original source. During this transportation, the particle breaks into smaller grains and typically becomes rounded. Clastic sedimentary rocks are further classified according to grain size: shale contains clay-sized grains; siltstone contains silt-sized grains; sandstone contains sand-sized grains; conglomerate contains grains that are pebble to boulder-sized.

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Clastic sedimentary rocks: shale (left), sandstone (center), and conglomerate (right).

Biogenic sedimentary rocks are those that form through biological activity. By far the most common example is limestone, which forms by the production of calcium carbonate by algae and invertebrate animals for shells.   Other examples include dolomite, which forms by the same process as limestone, and chert, which forms by the accumulation of silica-producing organisms on the sea floor.

Chemical sedimentary rocks form by non-biologically induced precipation of minerals. Examples include sinter and travertine, which consist of silica and calcium carbonate respectively, precipitated from hot water at thermal springs. Another important example is bedded salt, which forms today by evaporation in closed desert basins.

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Tilted sedimentary rocks –started out horizontally.

You can’t see the bedding in the rock samples shown above, but if you were to stand back from an outcrop of sedimentary rocks, you probably could see the bedding. That’s because most individual samples don’t go across bedding but instead come from individual beds.

 

 

Metamorphic Rock –more details

Most metamorphic rocks are classified according to their grain size and the resulting nature of their foliation. Slates are the finest grained metamorphic rock, followed by phyllite, schist, and gneiss, being the coarsest grained. Gneiss is especially distinctive because most of its crystals are readily visible and its foliation is marked by bands of different minerals. In general, crystal size corresponds to the metamorphic grade, or intensity, with the most coarsely crystalline rocks being of the highest grades.

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Metamorphic rocks. From left to right: slate, phyllite, schist, gneiss. Note that each rock has layering (foliation) that is caused by a parallel arrangement of platy minerals within the rock.

And then there are metamorphic rocks that form just because of high temperatures, typically because they were heated by the intrusion of a nearby igneous body. This type of metamorphism, called “contact metamorphism” is a common origin for non-foliated marbles and quartzites. Marble forms by contact metamorphism of limestone and dolomite; quartzite forms by contact metamorphism of sandstone.

The photo on the below shows the igneous rock diorite intruding the sedimentary Helena Dolomite in Glacier National Park, Montana. You can see how contact metamorphism has turned the dolomite next to the intrusion into a white marble. Ooooh!

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Intrusive “sill” of diorite and the resulting contact metamorphism of adjacent gray dolomite to white marble in Glacier National Park, MT.


For more, higher resolution photos of each feature or rock type, try doing a geology keyword search for any of the rock types or features described here. Some useful keywords are “igneous, intrusive, volcanic, metamorphic, sedimentary, phenocryst, tuff, pumice, or volcanic glass” –or any others you can think of. Enjoy!

 

Mauna Loa Volcano, Hawai’i –Earth’s largest active volcano

To get an idea of the immensity of Mauna Loa Volcano, take a look at the photo below. That rounded shape continues from its summit area at 13,678 feet above sea level to about 18,000 feet below sea level –and then another 25,000 feet or so below that because the mountain has sunk into the oceanic crust. It’s unquestionably the world’s largest active volcano.

Mauna Loa Shield Volcano

Profile of Mauna Loa Shield Volcano from… Mauna Loa Shield Volcano! (Geologypics: (170919s-15))

Briefly, Mauna Loa’s made of basalt. Basaltic lava flows, being comparatively low in silica, have low viscosities and so cannot maintain steep slopes, resulting in broad, relatively low gradient volcanoes called shields. With just a little imagination, you can see how Mauna Loa’s shape resembles that back side of some shield one of King Arthur’s Knights might carry into battle.

Read more…

Geologypics.com– A new (and free) resource for geological photographs

What better way to kick off my new website than to write about it on my blog? To see it, you just need to click on the word “home” in the space above. Or you can click the link: geologypics.com.

Here’s part of the front page:
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As it says, the site offers free downloads for instructors –and for anybody who’s craving a good geology photograph. It’s my way of contributing to geology education –showing off some of our landscape’s amazing stories and providing resources for other folks who want to do the same.

I think the best part of the whole site is that red button in the middle of the home page. It says “Image Search by Keyword”.

Right now, there are more than 2200 images you can search for — all of which are downloadable at resolutions that generally work for powerpoint. If you search for “sea stack” for example, you’ll get 38 hits –and the page will look like this:

Sea Stack search

First page of sea stacks when you search on the term.

 

Notice that ALL the photos are presented as squares–which works for most photos, but not all. To help mitigate that, the photos with vertical or panorama formats say so in their title, so you know to click on them to see the whole image. Take the photo in the upper center, for example –it’s got a  vertical format. Here it is:vertial image

 

A more detailed caption below the photo, along with its ID number appears at the bottom of the pic. This particular image is the chapter opener to the Coast Range in my new book “Roadside Geology of Washington“, which I wrote with Darrel Cowan of University of Washington.

There are also galleries –a chance to browse a variety of images without having to think of keywords. Similar to the search, they’re presented as squares so you need to click on the photo to see the whole thing.

 

Here’s what the photo gallery page looks like (on the left), followed by part of the “glaciation” page you’d see if you clicked on “glaciation”.  Woohoo!

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part of Galleries page (left) and part of Glacial page (right)

 

Then there’s the “About” page, which gives some information about me and details my policies regarding use of the images (basically, you can download freely for your personal, non-commercial use if you give me credit; if you want to use the image in a commercial publication you need to contact me to negotiate fees). There’s also a “News” page, that gives updates on the website. There’s a contact page from which you can send me emails. And the blog? It goes right back to here!

And finally, if you’re looking for a great web designer? Try Kathleen Istudor at Wildwood SEO –she created the site and spent hours coaching me on how to manage it.

Enjoy the site!

 

Summarizing Washington State’s Geology –in 19 photo out-takes

Washington State displays such an incredible array of geologic processes and features that it makes me gasp –which is one reason why writing “Roadside Geology of Washington” was such a wonderful experience. I also got to do it with my long-time friend and colleague (and former thesis advisor at the University of Washington) Darrel Cowan. The book should be on bookshelves in mid-September –and I can’t think of a better way to celebrate than by summarizing Washington’s amazing geology with a bunch of out-take photos –ones that didn’t made it into the book or even to my editor. Like the photo below:

Mount Baker, Washington (150916-4)

Mt. Baker, a glaciated stratovolcano in northern Washington State.

Mount Baker’s a stratovolcano that erupted its way through the metamorphic rock of the North Cascades. I took the photo from the parking lot at a spot called Artist’s Point –at the end of WA 542 –and my editor nixed it because I already had enough snow-capped volcanoes in the book.

On the cross-section below–which includes elements of Oregon as well as Washington, Mt. Baker is represented by the pink volcano-shaped thing labelled “High Cascades”. The following 15 or so photos illustrate most of the other features on the cross-section –so together, they illustrate much of the geology and geologic history of the state!

Cross-section across PNW

Generalized cross-section across Washington and Oregon.

Washington State and geologic provinces

Washington State and geologic provinces.

A quick note about organization: I’m separating the images according to their  physiographic province. There are six in Washington: Coast Range, Puget Lowland, North Cascades, South Cascades, Okanogan Highlands, and Columbia Basin.

 

Coast Range:
As you can see in the cross-section, the Coast Range borders the Cascadia Subduction Zone and consists of three main elements: the Hoh Accretion Assemblage in yellow, Siletzia (called the “Crescent Formation” in Washington) in purple, and the post-accretion sedimentary rock in brown. Siletzia is the oldest. It was thrust over the Hoh Accretion Assemblage, which is still being accreted at the subduction zone. The post-Accretion sedimentary rocks were deposited over the top of Siletzia after it was accreted about 50 million years ago.

And here are some photos! Siletzia formed as an oceanic plateau and so is characterized Read more…

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