Episode 131 – Volcanoes

Listen to Episode 131 on PodBean, YouTube, Spotify, or your podcast-player of choice!

When molten rock finds a path to Earth’s surface, the result can include lava seeps, gas leaks, explosions of ash, the reshaping of landscapes, the alteration of the climate, the elimination of ecosystems, and perhaps even in certain cases, widespread extinction. This episode, we talk (at length) about the geological and biological impacts of Volcanoes.

In the news
Ankylosaur braincase preserves evidence of these dinosaurs’ senses and lifestyle
Incredible new fossil site records an ancient Australian rainforest
Mysterious horse-like animal might be the oldest known domesticated hybrid
Tonga witnesses the largest volcanic eruption in 30 years (Read more here)

Varied, Volatile, Violent

The term volcano might make you think of an exploding mountain, but the term is often used more broadly than that to refer to any vent or opening in the Earth that allows molten rock, gases, and tephra (solid rock in the form of ash or larger chunks) to escape to the surface. Volcanoes are extremely diverse. Some seep slow lava flows, while others erupt in massive explosions; some erupt only once, while others erupt repeatedly; some eruptions are so small you’d barely notice them, and some are so large their impacts can be felt around the globe.

Top left: Sabancaya volcano in Peru produces an ash plume during an explosive eruption. Image from the
Galeria del Ministerio de Defensa del Perú, CC BY 2.0
Top right: Mayon volcano in the Philippines produces lava flows in an effusive (non-explosive) eruption. Image by Tryfon Topalidis, CC BY-SA 3.0
Bottom left: The volcano Skjaldbreiður in Iceland is a shield volcano, formed from successive vast layers of flowing and cooling lava. Image by Reykholt, CC BY-SA 3.0
Bottom right: The Karapinar volcanic field includes a variety of volcanic vents, including numerous cinder cone volcanoes and craters from past eruptions. Image by Christian1311, CC BY-SA 4.0
Volcanic activity (represented in red on this map) is extremely common on land and in the ocean. Volcanoes commonly form at plate boundaries, particularly near subduction zones and spreading centers.
Image: NASA
Evidence of past volcanic activity is everywhere. In fact, most of the Earth’s crust is volcanic in origin.
Top: Lava flows cool into layers of igneous rock on the Big Island of Hawaii. Image by Brocken Inaglory, CC BY-SA 3.0
Middle: These layers of ash came from Izu Oshima volcano in japan, laid down on uneven ground. Image by Stanisław Raczyński, CC BY 3.0
Bottom: Lake Toba is a flooded caldera, a crater left behind by a supervolcanic eruption. Image from Visions of Domino, CC BY 2.0

Living with Volcanoes

Volcanoes are an essential part of Earth’s rock cycle and carbon cycle, and they can often provide sources of heat and soil nutrients. That said, they’re also extremely dangerous, producing a long list of hazards including (but not limited to): hot lava, ash, flying rocks, pyroclastic flows, toxic gases, landslides, mudslides, avalanches, earthquakes, tsunamis, and more. Some volcanic activity, like the most dramatic eruptions of Krakatoa, Pinatubo, and Tambora, had such an impact on the atmosphere that they lowered global temperatures for up to a few years. Needless to say, a world with volcanoes is a dangerous one for life.

Despite the danger, many organisms make their homes near or even atop volcanoes.
Left: Crater lake of Mt. Pinatubo, less than 20 years after its massive eruption in 1991, seen here supporting an ecosystem of local plants (and surely animals). Image by ChrisTomnong, CC BY-SA 3.0
Right: An ʻōhiʻa lehua tree flowers on a field of cooled lava flows on Kilauea, Hawaii. Image by Brocken Inaglory, CC BY-SA 3.0

There is a field of science called disturbance ecology, which studies how ecosystems respond to disastrous changes such as fires and storms. A subset of this discipline is volcano ecology, which has been examined thoroughly in certain recent eruptions such as those of Mt. Pinatubo (1991) and Mt. St. helens (1980).

Volcanoes are not normally very good for fossil preservation, but there are exceptions.
Left: A rhinoceros preserved in volcanic ash at Ashfall Fossil Beds in Nebraska. This entire ecosystem was preserved like this after an eruption 12 million years ago. Image from Wikimedia Commons, CC BY-SA 2.0
Right: The famous footprints of Laetoli, including early hominin tracks, were preserved in ash-y sediment in a volcanic landscape. Image by Wolfgang Sauber, CC BY-SA 4.0
Other volcanic fossils we mention in this episode include lava-preserved dinosaur tracks, a rhino skull in a pyroclastic flow, and the famous Blue Lake Rhino.

Volcanoes certainly have a dramatic impact on life. Eruptions can damage ecosystems, destroy entire islands, or render landscapes uninhabitable, if only temporarily. The enormous eruption of Toba 74,000 years ago has even been suggested to have hindered the early advancement of humans, although this hypothesis has been challenged by recent studies.

Large Igneous Provinces

Throughout Earth history, there have been periods of volcanic activity that lasted for millions of years, covering a region in hundreds of thousands of cubic kilometers worth of lava. These volcanic epochs can dramatically impact life, climate, and the landscape. The vast plots of volcanic rock these events leave behind are called Large Igneous Provinces.

Large igneous provinces (LIPs) are surprisingly common. This map shows some of the most famous known LIPs on land, and many more exist on the ocean floor. Image by Williamborg, CC BY-SA 3.0
Satellite image of the Deccan Traps in India, a large igneous province that forms the foundation of this geologic region. The Deccan Traps were erupted about 66 million years ago.
Image by Planet Labs Inc. CC BY-SA 4.0

It has been noted by geologists and paleontologists (and on our podcast) that Large Igneous Provinces have a habit of lining up in time with mass extinctions and other major events. Just on our podcast, the possible impact of LIP volcanism has come up while discussing the end-Cretaceous mass extinction, the end-Triassic mass extinction, the Permian mass extinction, the Devonian mass extinction, Snowball Earth, and more. In some cases, long periods of intense, repeated volcanic activity are linked to climate impacts that are thought to have been major drivers of extinction. In other cases, the connection is less certain. Not all extinctions coincide with the formation of large igneous provinces, and vice versa, but the consistency of their coincidence is probably not … well, a coincidence.

Learn More

For lots of details about the workings of volcanoes, check out Oregon State’s website, the Encyclopedia Britannica, and the USGS.

You Don’t Need to Worry About Yellowstone (or Any Other Supervolcano) [VIDEO]
The Toba eruption might not have hurt early humans as much as some thought. Read more here and here.

Volcano Ecology:
A 2015 overview of the subject (technical, paywall)
A case study at Mt. St. Helens, 1985 (technical, paywall)
A case study at Mt. Pinatubo, 2020 (technical) + press release

Large Igneous Provinces and Mass Extinction (technical, paywall)

If you enjoyed this topic and want more like it, check out these related episodes:

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One thought on “Episode 131 – Volcanoes

  1. Tracy Basham January 24, 2022 / 11:38 am

    Awesome job guys! As usual, I enjoyed this immensely.


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