PlanetGeo: The Geology Podcast Chris and Jesse

Join us as we interrupt our water series re-release to talk about a major current event - the eruption of Hunga Tonga-Hunga Ha'apai volcano in Tonga.
It was a huge eruption in the South Pacific from a very active volcano.  Its had some smaller eruptions in the last few months, but Saturday morning took the lid off.

In fact, some instrumented Cascade volcanoes - Mt Hood, Mt Saint Helens, and Mt Ranier, detected infrasound records (essentially specialized microphones).  The second longer but lower-magnitude signal that shows up later in the plot - is the airwave passing by the station again -- having come from the other direction!  That’s right, the airwave has wrapped around the planet!  The first wave traveled a distance of ~8500 km (~5300 miles).  The second traveled ~32,500 km (20,200 miles)!  In fact, barometers at O'hare airport in Chicago picked up the compression sound waves.
You may be wondering: why was there a volcano here in the first place? The answer is: plate tectonics! Tonga is one of the volcanic islands located on top of the Tonga Kermadec subduction zone! This is the convergent plate boundary where the Pacific Plate sinks below the Australian Plate. The Pacific Plate is made of old, cold, and dense rock material that sinks beneath the Australian Plate, where the subducted rocks heat up and melt as crust is recycled. The water and other volatiles rise up as the rocks are melting -- contributing to the "Big Boom" of the eruption.
Why are the eruptions so violent?  Potentially?  It’s not always violent, but about every thousand years, it let’s loose with huge eruptions.  Why doesn’t the cool ocean water cool the magma?  If magma rises slowly, there will be a thin layer of steam between the water and the magma.  This will allow the outer edge of the magma to cool.  If the magma rises fast, the magma is in direct contact with the water.  The result is much like a weapons grade chemical explosion that starts a chain reaction where fresh magma is exposed to new water.  So this is a combination of magma/water interaction as well as gas charged sticky magma that has been building for the last 1000 yrs.  By studying deposits from past eruptions, we know that we might be in for several weeks (or years) of intense volcanic activity.  
 The violence of the blast triggered tsunamis.  About 1.2 meters (4 feet) on the country of Tonga.  Hard to get a clear picture of devastation yet because of ongoing eruptions.  I don’t think this story is done yet.
Ash reached 20km into the sky and it produced a ton of lightning ~ 100 bolts/sec!

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Jesse and Chris are recording face to face in Michigan.  Join us as we follow the water issues theme in our re-release series.

Show notes below:
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.






 
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This is a re-release of a much earlier episode on Dams.  In our newly recorded intro, Jesse and I are in person and sitting across from each other as we give a little prelude to the episode.  We also decide to re-release our dams revisited episode from earlier this past summer.  Enjoy!

In this episode we cover....you guessed it, dams!  Dams are incredible manmade features that can not only dominate the landscape but also dominate the river system and fundamentally change how the rivers operate. 

We discuss everything from the amount of dams in the United States to major dam failures in the recent past, and highlight some of the basics of how dams fundamentally affect streams when they are installed. 

Here are some highlights of the statistics we cover! 
There are roughly 91,000 Dams in the USThey Impound over 600,000 miles of river or 17% of riversThe average age is 59 yearsThe number of high-hazard potential dams is over 15,000 and increasingIt is estimated that over 70 billion dollars is needed to properly upgrade these dams.  For perspective, 425 billion dollars are spent each year on Road Infrastructure.  About 75% of that comes from state and local governments.  25% comes from Federal.Dam regulation is largely up to each state and each person is responsible for about 200 dams.All too many are suffering from a neglected investment in infrastructure.Dams are this interesting intersection between geology, engineering, government oversight, and humanity.So why do we build them?  So many reasons: hydroelectric, irrigation, flood mitigation, recreation, municipal water




 
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A geology re-release of our talk about the worlds water and the issues we face.  Jesse and Chris are face to face recording this time which presented some challenges as you'll soon hear.  We had fun re-capping our water episode and we hope you have fun too as you hopefully learn a bit.

In this episode, Jesse and Chris talk about water.  That's right - water.  Where is the worlds water?  We begin by lumping all of the worlds water into 6 geological basins: oceans, glaciers, groundwater, lakes, atmosphere, and rivers.  We then assign relative percentages to each reservoir and then demonstrate how much water each would hold if all of the worlds water were scaled down to 5 gallons (19 Liters).

What comes to light is that less than 1% of all the worlds water is useable for human consumption - less than a half of a cup on a 5 gallon scale!  That "1/2 cup of water" is enough to keep 9 billion people alive, but it is not evenly distributed over the planet.

We use the Great Lakes in the Mid-West United States to illustrate the "haves and have nots".  The Great Lakes contain 21% of all the standing fresh surface water on Earth.  Despite having this incredible amount of water, the Great Lakes Basin is already dealing with water issues.  Our groundwater is being depleted and our standing water is being diverted.

We use the Chicago River diversion to illustrate some of the issues and concerns about moving Great Lakes water out of the Basin.  We also use Waukesha, Wisconsin as an example of an area that has a poor groundwater source but has been granted access to Great Lakes water to avert their needs.

Although we talk a lot about the Great Lakes region in this episode, the issues here are an analogy for the entire planet.  World population might reach 9 billion in 20 years.  Fresh water is finite and we need to be aware of the issues we will face - and are already facing while we still have time!





 
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This is Part 4 of our re-released Climate and Energy series!  We are on a break right now, but there is always great geoscience information to learn about!

Today we get to talk about something really relevant to our everyday lives, and the future - Geothermal Energy!

Geothermal Energy is a term that means a few different things, but it all relies on the Earth being somewhat hot.  So, before we dive into the question of what Geothermal Energy is, we need to figure out why the Earth is hot!

The Earth produces a ton of heat, which is really important to understand how our planet operates over long times (remember plate tectonics??).  The heat comes from several sources, and some of it is left over from when the Earth formed - so some of the geothermal energy is tapping into 4.5 billion-year-old heat!

Geothermal energy takes two major forms: 1) passive geothermal heat pumps, often used in residential houses like Jesse's and 2) more active geothermal power plants that use lots of heat from the Earth!

As usual, follow us on social media and let us know what you think by sending us an email!




 
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This is Part III of our re-released Climate and Energy series!  We are on a break right now, but there is always great geoscience information to learn about! 

Did you know that nuclear fission reactions are natural?  Uranium fission drives many types of nuclear power plants as well as nuclear weapons.  However, these types of reactions occurred on Earth naturally, just billions of years ago.  Today, we discuss the Oklo natural fission reactors in Gabon, Africa.  

These natural reactors are not only amazingly cool, but they have a really interesting discovery story and they can teach us a lot about the overlap between nuclear physics and geoscience, how uranium deposits form, and what Earth's ancient atmosphere looked like! 

These are important for several reasons:
Geology and nuclear physics have a very intimate relationship. Basically all radiometric dating we use on Earth was developed on the back of research on Uranium nuclear physics and research into nuclear weapons/reactors. Geoscience and national security are intimately related: Nuclear forensics, or using isotope analyses to look for people enriching uranium, use the same techniques and instruments as geochronologyMany PhD geoscientists go to work in national security labs/jobsThese natural nuclear reactors help us explain Earth’s history and where Uranium deposits occur.  
Another cool feature of these ancient nuclear reactors is that they may have looked much like geysers in Yellowstone National Park!  They were moderated by natural groundwater, and they cycled on and off in ~30 minute cycles. 

All told, these natural nuclear reactors are one of the single coolest geoscience factoid we know of! 




 
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