The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on a weekly schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Tuesday, February 13, 2018

Episode 387 Geology of Beer


It isn’t true that all geologists drink beer. But many do, and I’m one of them. Today I’m going to talk about the intimate connection between geology and beer.

Beer is mostly water, and water chemistry has everything to do with beer styles. And water chemistry itself depends mostly on the kinds of rocks through which the water flows. You know about hard and soft water – hard water has more dissolved chemicals like calcium and magnesium in it, and while salts of those chemicals can precipitate out of hard water, making a scum on your dishes, they also can be beneficial to development of bones and teeth. In the United States, the Midwest and Great Plains have some of the hardest water because of the abundant limestones there, and in Great Britain, southern and eastern England have harder water than Scotland for similar reasons.

But it wasn’t limestone that made Burton-upon-Trent a center of brewing in the 19th Century, when it was home to more than 30 breweries. The water there is rich in sulfate which comes from gypsum, calcium sulfate, in the sandstone underlying the region. Those sandstones are Permian and Triassic in age, representing a time when much of the earth was arid. Those dry conditions allowed gypsum to crystallize in the sediments. Gypsum is much more soluble than limestone, and the slightly acidic waters of Burton help with that. Burton water has ten times the calcium, three times the bicarbonate, and 14 times the sulfate of Coors’ “Rocky Mountain Spring water” in Colorado. That certainly makes Coors’ Burton brewery product rather different from that made in Colorado.

In fact, the addition of gypsum to beer is called “Burtonization.” This increases the hops flavor, but more important to history, sulfates act as preservatives in beer, enough so that Burton brews of pale ales could survive the long trip to British India, giving us the India Pale Ale style of beer. Not from India, but brewed with sulfates derived from gypsum in Britain’s rocks.

That slight acidity in Burton’s water depends on the calcium and magnesium content, and also lends itself to extracting sugars from malted barley in the mashing process. Calcium and magnesium also help yeast to work its magic. Today, home brewers can buy “Burton Water Salts” to imitate the product from England.

Truman, Hanbury, Buxton & Co., Black Eagle brewery, Derby Street, Burton-upon-Trent, in 1876,
from University of London
Less hoppy beers often originated in areas where the sulfate content of the water was low. Pilsen in the Czech Republic, home to pilsner beer, has almost no sulfate and only 7 parts per million calcium in its water, compared to around 300 for Burton. Pilsen is in an area of metamorphic rocks that don’t yield the typical hard-water-making elements.


The presence of Carboniferous age limestones in Ireland make waters that are high in calcium and carbonate, but they lack the sulfate of northern England. Together with other differences, that makes the area around Dublin ideal for making a stout porter known today as Guinness.

After water, it’s the soil that makes the most difference to beer. Hops can grow in a wide range of soils, even the decomposed granite we have here in Butte, but the thick, well-drained soils of Washington and Oregon, weathered from volcanic rocks, make those states the source of 70% of the hops grown in the United States.

The surge of craft breweries in the United States has given rise to some interesting geological names for brews. Great Basin Brewing in Reno and Sparks, Nevada, has Ichthyosaur IPA, known as Icky, as well as Orogenesis, a Belgian-style amber ale. Socorro Springs, in New Mexico, brews Isopod Pale Ale and Obsidian Stout is available from Deschutes in Oregon.  You can get Triceratops Double IPA at Ninkasi Brewing in Eugene, Oregon, and Pangaea Ale at Dogfish Head in Delaware. And even though it’s more chemical than geological, we shouldn’t leave out Atomic Ale’s Dysprosium Dunkelweizen, made in Richland, Washington. Dysprosium is a rare-earth element found in the phosphate mineral xenotime and other stranger minerals.

San Andreas Brewing Company, near the fault in California, boasts Oktoberquake and Aftershock Wheat.

And I’m undoubtedly prejudiced, because I’m the House Geologist at Quarry Brewing here in Butte, which probably has the best mineral collection in a brewery in the United States, but I think their collection of geological names for their beers is unexcelled: Shale Pale Ale, Galena Gold, Open Cab Copper, and Gneiss IPA, and seasonals including Albite, Basalt, Bauxite, Calcite, Epidote, Halite, Ironstone, Porphyry, Opal Oktoberfest, Schist Sour, Rhyolite Rye Pale Ale, Pyrite Pilsner, and more. Mia the bartender and I tried to come up with a fitting name for a 50-50 mix of basalt and gneiss. I wanted it to be charnockite, but we ended up calling it Mia’s Mixture.

Next time you enjoy a beer, thank geology!

—Richard I. Gibson

Image: Truman, Hanbury, Buxton & Co., Black Eagle brewery, Derby Street, Burton-upon-Trent, in 1876 from University of London


Sunday, February 11, 2018

Paleozoic Vertebrates compilation


Ganoid fish from an old textbook (public domain)
Running time, 1 hour. File size, 70 megabytes.


This is an assembly of the 15 episodes in the original series from 2014 that are about Paleozoic vertebrates.

I’ve left the references to specific dates in the podcast so that you can, if you want, go to the specific blog post that has links and illustrations for that episode. They are all indexed on the right-hand side of the blog.

Thanks for your interest and support! 

Tuesday, February 6, 2018

Episode 386 Dynamic Topography



What is dynamic topography? Well, it depends on who you ask. Dynamic topography is similar to other terms, like uplift, that have been used in so many different ways that you really have to look at the document you’re reading to understand what the author is talking about. This term has been applied to places around the world, like the Colorado Plateau in the United States, South Africa, the Aegean, and East Asia, which makes it even more complicated to tease out its meaning.

Most broadly, dynamic topography refers to a change in the elevation of the surface of the earth in response to something going on in the mantle. This “something” can include both the flow of the mantle, as well as differences in mantle temperature or density. For the purposes of this podcast, I will use a more strict definition: Dynamic topography is the change in the elevation of the surface of the earth in response to the upward or downward flow of the mantle.

How much higher or lower can dynamic topography make the earth’s surface? Well, that’s a matter of debate. Earlier studies have suggested that several kilometers, or over 6000 feet of modern elevations can be explained by things going on in the mantle. More recent work instead suggests that dynamic topography creates changes of at most a three hundred meters, or a thousand feet.

A good example of a place where this process is thought to be active is Yellowstone. As Dick Gibson discussed in the December 19th, 2014 episode, Yellowstone is thought to be a hot spot. That is, an area of the earth where hot material moves from deep within the mantle to the base of the crust, causing significant volcanism at the surface of the earth. Other well-known hot spots are located in Hawaii, and Iceland.

So how can a hot spot like Yellowstone cause dynamic topography? Well, you’ve probably seen a similar process at play the last time you played in a pool or a lake. Think of the surface of the pool like the surface of the earth. If you start moving your hands up and down under water, the surface of the pool starts to move up and down. If you ever tried to shoot a water gun upwards underwater when you were a kid, you probably remember it pushing up the surface of the water, and being disappointed that it didn’t shoot out at your friend or sibling. As an adult, you could try holding a hose upwards in a pool. Again, it probably won’t shoot out, but will gently push upwards on the surface of the pool.

Dynamic topography concept. © Commonwealth of Australia (Geoscience Australia)
 2017, used under Creative Commons Attribution 4.0 International Licence 
The principle for a hot spot creating dynamic topography is the same. The flow of the mantle pushes upwards, warping the crust and increasing the elevation of the earth’s surface above the hot spot. Near Yellowstone, this results in an area of high elevation which lies next to the Snake River plain.

But Dynamic Topography doesn’t just cause increases in elevation, it can also pull the earth’s surface downward. In North America, dynamic topography is thought to have been in part responsible for the creation of the Cretaceous interior seaway. 

As a reminder, the Cretaceous interior seaway was a shallow sea that covered parts of western North America, in middle to late Cretaceous time, about 100 to 79 million years ago. Its size varied, but at its greatest extent the seaway stretched through Texas and Wyoming in the US, and Alberta and to the Northwest Territories in Canada. It was widest near the US-Canadian border, where it stretched from Montana to western Minnesota.

Low elevations in western North America that allowed the ocean to flood in and form this shallow sea may have been caused by downwards flow in the mantle. This downwards flow was likely caused by oceanic crust that was subducted at the western margin of North America. That is, oceanic crust that went underneath the North American plate and into the mantle. Because this crust was part of the Farallon oceanic plate, it is often referred to as the Farallon slab.

As oceanic crust associated with the Farallon plate continued to sink into the mantle, it continued to cause changes in the elevation of North America. This drop in elevation likely decreased in size as the Farallon slab moved towards the eastern edge of North America, and deeper into the mantle.

Since Eocene time, or about 55 million years ago, dynamic topography associated with the Farallon slab is thought to have been in part responsible for lower elevations in the eastern United States. A wave cut escarpment called the Orangeburg Scarp is now located 50 to 100 miles inland from the coasts of Virginia, Georgia and the Carolinas. It formed at sea level and now lies up to 50 meters, or about 165 feet above the modern coast line. In fact, a good part of the southeastern US to the east of this escarpment contains marine sediments, and smooth topography as a record of its time underwater.

Differences in the elevation of the Orangeburg Scarp along its length suggest that rather than just going up and down, the Atlantic coast experienced a broad warping caused by mantle flow. The most recent phase of warping brought this area to modern elevations, as warm material moved into the upper mantle beneath the Atlantic coast. This warm material helped push the crust up to higher elevations, creating the southeastern US as we see it today.

This example also highlights an important part of dynamic topography: If you are already at really high or really low elevations, you might not notice it much. If you are near the coast, it can have a big impact as the sea starts to flood in and out due to changes in the mantle. Provided of course, you’re there for the millions to tens of millions of years it takes for the mantle to flow this way and that. That’s why geologists typically rely on the rock record to provide evidence for processes like dynamic topography.
—Petr Yakovlev

This episode was recorded at the studios of KBMF-LP 102.5 in beautiful Butte, Montana. KBMF is a local low-power community radio station with twin missions of social justice and education. Listen live at butteamericaradio.org.

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