PlanetGeo: The Geology Podcast

Latest Episodes:

The Great Salt Lake: Historically Low Water Levels Jul 29, 2021

Show notes

For some background listen to our previous episode on hard water and why oceans are salty!
Join us on this GeoShort as we discuss the Great Salt Lake, which is going through a period of very, VERY low water levels. The average depth of the Great Salt Lake in Utah is now only 2.4 inches, or 5 cm! This low water level is mostly caused by the drought in the SouthWestern US, and impacts communities around the Great Salt Lake.
In this GeoShort we discuss why salty lakes occur, which is due to the fact that water coming into the lake can only leave by evaporation. And salt doesn't evaporate...it crystallizes. So, when water leaves, the salt stays behind and it just keeps building up in the lake. The particular geology of the SW United States means that there are several large rivers that feed into basins that do not feed into the ocean.
Check out our previous episode on Hard Water to learn how salt gets into water, and why oceans are salty! Remember, although the common table salt (NaCl) is part of the 'salt' we are talking about, there are other salts out there and we geologists use the term broadly!
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On the app you can get tons of free content, exclusive images, and access to our Geology of National Parks series.
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Geysers and Hot Springs: Why They Matter with Examples From Yellowstone National Park Jul 22, 2021

Show notes

Today we talk about Geysers! And Hot Springs, Mudpots, and Fumaroles! These are extraordinary features that give any landscape a pretty dramatic look. They are also very prevalent in Yellowstone National Park, and we give some key examples from that area.
Hydrothermal features are really important to understand and monitor. So important that the United State Congress passed a law requiring all National Parks to monitor and document hydrothermal features! Hydrothermal features allow us to track heat and water deep within the Earth. This is becoming more important because heat and water give us Geothermal energy systems that might be growing during the coming energy transition.
Join us for a wide ranging discussion on hydrothermal features, how they work, and what they tell us about the Earth!
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Rock Circles: Geologically Curious Phenomena (GeoShort) Jul 15, 2021

Show notes

Our GeoShort today focuses on Spherical Weathering, where normal rocks are turned into round shapes by chemical erosion.
Many rocks have cracks in them, called joints, and these joints often break the rocks up into little cubes or rectangular prisms. Cubes and prisms have a high surface area relative to their volume, and the corners especially.
So fluids that have weak acid in them preferentially eat away at the corners, eventually turning the cube of rock into a perfect sphere! Spheres have the lowest Surface Area/Volume of any shape, because they have no corners or edges left. The rock just gets made into a smaller and smaller sphere then.
While spherical weathering is not a common process, it is not rare either. So, keep an eye out when you are outside next, you may find some Spherical Weathering near you!

Dammed Up Again: Streams and Dams Part Two Jul 08, 2021

Show notes

We liked talking about dams so much we did it again! Join our discussion on streams, how the normally operate, and how dams disrupt the way that streams function.
We highlight a few things in this episode, including a recent Eos article on sediment accumulation behind dams - expertly written by Tullos et al., the Paonia Reservoir where sediment accumulation has filled in the reservoir in record time, and another article on contaminated sediment releases from the Milltown Dam and the Hudson River that have caused big problems in the past, written by James Evans.
Chris also gets his long but warranted rant on the famous Aswan High Dam, and key example of the debates around the pros and cons of dams.
Also check out our previous episode on Dams at this link or anywhere you get your podcasts.

Big Valuable Crystals: Pegmatites (GeoShort) Jul 01, 2021

Show notes

What type of rock has really big minerals and lots of uncommon elements? It's a pegmatite! Pegmatites contain lots of important elements and minerals, both for our economy and for mineral collectors.
Join us for a tour of pegmatites. We give quick low-down on how pegmatites form. They contain really large mineral grains, which usually implies that they cooled slowly. But, pegmatites form from the leftover fluids from magma chambers and contain all the uncommon (or unpopular!) elements that get concentrated. Once they reach a certain concentration they form rare minerals that are concentrated in things like Lithium, Cesium, or Beryllium!
The minerals in pegmatites grow so fast because the fluid they grow in is much less viscous (more watery) than magma. This means that atoms and ions can diffuse much more quickly to the sites of mineral nucleation, allowing for massive (really really massive, up to 30 ft) crystals of minerals like spodumene and beryl to form.

The Spartans Last Stand: Geology of the Hot Gates Jun 24, 2021

Show notes

Have you ever watched the movie 300 or heard of the Spartans making a stand against the Persian Empire? It's an amazing story right...but it has some amazing geology behind it too.
Geology has influenced historical events in momentous ways, and here on PlanetGeo we are going to start highlighting these ways. This incredible story of the Hot Gates is just the first part of that series.
In this episode we are going to cover

Let’s start out with the words: Hot Gates. First, the Gates part of that. What formed the gates? Well it’s a fault like the Grand Teton National Park, and the tectonics of this region are really complex! We will start narrow (at the gates themselves) and zoom out to the broader region and talk about how complex plate tectonics can be on the 3D surface of the planet.
We will talk about the Hot part of the Hot Gates, and highlight some hydrothermal activity in the region. This includes hot springs, steam, and volcanoes!
Lastly, the Hot Gates don’t exist anymore. The planet is always changing, sometimes rapidly. Sea level has changed over time in this region since 480 BC, 2500 years ago. The sea level change is not due to actual sea level changing though, it is due to a totally different process: the valley is filling up with sediment that pushes the shoreline back from the cliffs that used to form the Hot Gates. This is totally normal stream behavior in areas with active mountain belts!

So, here’s the backstory. The Persian Empire was massive and was interested in invading Greece. There were several major battles here but we are focusing on one in particular where 300 spartan warriors stood their ground against at least 50,000 persians and maybe many more (history is foggy here).

They were able to fend off so many adversaries by using the local geology to their advantage, they took a stand in the Hot Gates, which were a series of three narrow passes between a cliff face and the Aegean Sea. This is a really interesting part of geoscience in that much of history is shaped by geoscience.

Shasta Tourism (Geoshort) Jun 17, 2021

Show notes

We had such a great conversation with Dr. Andrew Calvert, Scientist-in-Charge of the California Volcano Observatory, that we decided to run it back one more time.
Mount Shasta is clearly a favorite of Dr. Calvert's, and is famous location for hiking, climbing, and skiing. However, it is not a National Park despite the best efforts of the famous John Muir, and is not a true tourist destination. When thinking about visiting Northern California, don't forget to check out Lassen Volcanic National Park to experience more amazing volcano geology! Also, check out our previous discussion with Dr. Calvert about Shastina, the spunky little sister to Mount Shasta. Shastina presents something of a geological conundrum as it doesn't quite fit with the rest of the Cascade volcanoes.
Here is a link to Dr. Calvert's research profile, and a short bio:

Education

Ph.D., University of California – Santa Barbara

Dissertation: Metamorphism and exhumation of mid-crustal gneiss domes in the Arctic Alaska Terrane

M.S./B.S., Stanford University (both degrees conferred June 1992)

Thesis: Structural Evolution and Thermochronology of the Kigluaik Mountains, Seward Peninsula, Alaska

Observing Volcanoes: Dr. Andrew Calvert, Scientist-in-Charge of CalVO Jun 10, 2021

Show notes

Today we have the great pleasure of interviewing Dr. Andrew Calvert, the Scientist-in-charge of the California Volcano Observatory. In this conversation we cover a huge range of topics from Mount Shasta, to how magmas form and become more silica rich, the role of federal institutes like CalVo in volcano hazard prediction and monitoring, and some details about potassium-argon (K-Ar, as argon-argon, Ar-Ar) geochronology using noble gases in minerals!
Dr. Calvert also gives and excellent description of how magnetometers are used to map lava flows on old volcanoes. This is an incredible tool that helps drive a deeper understanding of the volumes and rates of past volcanic eruptions, which is very valuable information that is used to help forecast volcano behavior!

Dr. Calvert is an excellent science communicator and has a wide variety of experiences studying volcanoes as well as directing observation and hazard prediction efforts. Join us for an amazing conversation with Dr. Andrew Calvert!
Here is a link to Dr. Calvert's research profile, and a short bio:

Education

Ph.D., University of California – Santa Barbara

Dissertation: Metamorphism and exhumation of mid-crustal gneiss domes in the Arctic Alaska Terrane

M.S./B.S., Stanford University (both degrees conferred June 1992)

Thesis: Structural Evolution and Thermochronology of the Kigluaik Mountains, Seward Peninsula, Alaska

Lava’s All You Need: Preview to Interview with Dr. Andrew Calvert (GeoShort) Jun 03, 2021

Show notes

Today we have a preview to our interview with Dr Andrew Calvert, Scientist in Charge of the California Volcano Observatory, also known as CalVO.
Dr. Calvart first fell in love with volcanoes as a young boy growing up in Idaho when Mount Saint Helens erupted. This was the first ash sample he ever collected, and he and Chris share this connection to volcanoes and their interest in geoscience.
In this GeoShort, Dr. Andrew Calvart walks us through a million years of geologic history of Mount Shasta in Northern California. He has collected samples from every lava flow coming from the volcano. A million years ago, Shasta didn't exist. About 700,000 years ago, Shasta began forming. But, similar to Saint Helens, it fell apart about 400,000 years ago. He also talks about how episodic Shasta is compared to many of the other Cascadia stratovolcanoes. It doesn't erupt as often as many of the others. Despite being very eposodic, it's not very explosive (usually). Dr. Calvart also explains how the magma beneath Shasta is not as viscous as other stratovolcanoes.

The Day the Dinosaurs Died: Dr. Ian Miller, Director of the Denver Museum of Nature and Science May 27, 2021

Show notes

Dr. Ian Miller is the Director of the Denver Museum of Nature and Science, now working with National Geographic as the Chief Science and Innovation Officer. Dr. Miller is a paleobotanist who has spent his career making amazing discoveries about the ancient Earth using fossils! In this interview Dr. Miller describes what the Earth looked and felt like in the minutes and days after a meteorite impact struck the planet, killing the dinosaurs and creating a global catastrophe! Dr. Miller and his research team have made incredible discoveries that help us understand how life began to recover from this disastrous event, as well as making inferences about the height of the Ancient Rocky Mountains!
If you are planning a trip in or around the Denver, Colorado area, you must listen to this episode to hear about the amazing geoscience story you are driving past! Here is an excerpt from Dr. Miller's profile, and we think you will agree that Dr. Miller is one of the best science communicators out there.
Raised on a llama ranch in rural Washington State, Ian Miller first discovered the lure of rocks and fossils while scavenging mine tailings for fool’s gold and pulling Miocene clams out of road cuts with his four younger brothers. As a geology major at The Colorado College, he discovered fossil plants, his research specialty, while working as an intern at the Denver Museum of Nature & Science. After a two-year stint as a field geologist in New Mexico, Ian attended Yale University, where he studied paleobotany and tectonics and received his PhD in 2007.

Miller spent 15 years at the Denver Museum of Nature & Science, most recently serving as the director of Earth and Space Sciences. During this time he studied fossil plants, paleoclimate, paleoecology, and tectonics, and he also co-led the Snowmastodon Project, which provided a new benchmark for understanding climate change in the American West.

Throughout his academic career, Miller has natural history experience on all seven continents and has been a lead scientist on major field expeditions in Madagascar and much of the western United States. He has published 30 peer-reviewed scientific articles and books on paleobiology and geology.

Beyond his work as a scientist, Miller has led museum initiatives aimed at deepening people’s connection with the natural world and unearthing major trends in new and existing audiences that will define the future of museums.

Miller is a previous board member of Snowmass Discovery, a peer-reviewer for multiple academic journals, and member of various scientific societies, including the American Association for the Advancement of Science, Geological Society of America, and International Council of Museums.

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