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In this two-hour special, renowned paleontologist Kirk Johnson takes us on an epic adventure through time at the polar extremes of our planet. Following a trail of strange fossils found in all the wrong places—beech trees in Antarctica, hippo-like mammals in the Arctic—Johnson uncovers the bizarre history of the poles, from miles-high ice sheets to warm polar forests teeming with life. What caused such dramatic changes at the ends of the Earth? And what can the past reveal about our planet’s climate today—and in the future? (Premiered February 5, 2020)

Paleontologist Kirk Johnson explores the dynamic history—and future—of ice at the poles.

Polar Extremes

Something big is happening to Earth’s climate, and the polar regions hold the key to understanding it. Join top scientists on the hunt for clues that tell a surprising story about our planet’s past...and preview where we might be headed.

The Polar Lab

Disastrous hurricanes. Widespread droughts and wildfires. Withering heat. Extreme rainfall. It is hard not to conclude that something’s up with the weather, and many scientists agree. It’s the result of the weather machine itself—our climate—changing, becoming hotter and more erratic. In this two-hour documentary, NOVA will cut through the confusion around climate change. Why do scientists overwhelmingly agree that our climate is changing, and that human activity is causing it? How and when will it affect us through the weather we experience? And what will it take to bend the trajectory of planetary warming toward more benign outcomes? Join scientists around the world on a quest to better understand the workings of the weather and climate machine we call Earth, and discover how we can be resilient—even thrive—in the face of enormous change.

Discover how Earth’s intricate climate system is changing.

Decoding the Weather Machine

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How an Underwater Volcano Produced a 60-Foot Tsunami

The most explosive event ever recorded on Earth—and the massive tsunami that followed.
On January 15, 2022, an underwater volcano erupted off the shores of the Pacific islands of Tonga—the most explosive event ever recorded on Earth. The blast triggered a massive tsunami with waves over 60 feet high. Here&#x27;s how it happened.
How an Underwater Volcano Produced a 60-Foot TsunamiPublished: May 25, 2023TAANIELA KULA: Felt like I’m witnessing Mother Earth’s might and power being released.NARRATOR: Eight hours later, the volcano stopped erupting. Then at 5:15 pm on January 15th, it produced an eruption over 70 times larger, exploding with the power of over 60-million tons of T.N.T. and triggering a series of tsunami waves that hit Tonga, Australia, Japan and the Americas.NARRATOR: This is the site of the volcano. All that is visible are two small islands, Hunga Tonga and Hunga Ha’apai.SHANE CRONIN: Looking behind me, you see, see the island of Hunga Ha’apai. So, that’s right on the edge of the volcano. The main volcano is actually over to the east. So, there’s this great big expanse of what looks just like completely clear ocean. We’re actually sitting right on top of the Hunga caldera. So, below us is actually the volcano.NARRATOR: Hunga Tonga-Hunga Ha’apai is a submarine volcano. Its two-and-a-half-mile wide crater sits at the top of a mountain nearly 6,000 feet tall, which is almost completely hidden under water. Only in two places is the crater wall high enough to break the surface, forming the two islands.Before the January 15th eruption, the volcano looked very different. The center of the crater was 2,300 feet shallower.SHANE CRONIN: During the first one and a half hours, it was ejecting material at a rate twice as much as the next biggest eruption that we know of. It threw out seven cubic kilometers of dense rock material.NARRATOR: That’s enough to cover the entire island of Manhattan in nearly 400 feet of debris.SHANE CRONIN: When a large amount of magma erupts from a volcano, large amounts of magma come out at once. And so that means that the top part of the volcano actually then sinks in on itself.NARRATOR: Shane’s idea is that as material erupted out of the magma chamber, it created a larger and larger void underground. When it could no longer support the weight of material above, the entire caldera dropped over 2,300 feet. Seawater flooded in, kick-starting tsunamis that radiated out from the volcano, an explanation of how the volcano could generate a 60-foot wave.

The most explosive event ever recorded on Earth—and the massive tsunami that followed.

Scientists Make Rare Discovery in Active Volcano

Volcanologists visit Tofua to study the volcano’s activity.
The volcano that produced one the most powerful eruptions in history has a twin, and it’s more active than scientists thought.
Scientists Make Rare Discovery in Active VolcanoPublished: May 11, 2023NARRATOR: Tonga is still recovering from the eruption of the Hunga volcano; now, scientists have discovered that its volcanic twin, Tofua, is far more active than satellites had led them to believe, a finding that has implications far beyond Tonga.SHANE CRONIN: We had a big eruption around 1,200 years ago, another big one around 800 years ago, and the most recent one around 400 years ago.NARRATOR: This pattern suggests Tofua should erupt again and soon.SHANE CRONIN: It’s fantastic. We’ve got a bit of a break in the weather. You can see how blue that gas is, coming off that volcano. When the color of the gas is blue, it’s sulfur dioxide.NARRATOR: This gas is released by the magma. The blue color is only visible if the levels of sulfur dioxide are high.SHANE CRONIN: So, I think the magma must be very close to the, close to the surface, actually. And this corresponds to what the locals have been reporting over the last couple of months is that there is a glow in the sky above Tofua, when there’s a cloudy evening.NARRATOR: The signs point to Tofua being far more active than the satellite readings suggest, but to know the level of the threat, the team needs more evidence. Taaniela will use a drone to investigate the active cone. While the rest of the team will collect vital readings, which need to be taken from inside the caldera itself.SHANE CRONIN: I’m going to try and get a position close to the plume. I don’t want to go underneath it because sulfur dioxide is actually quite lethal. We can then try to measure some of the output. This is what I’ve been lugging up the hill.NARRATOR: Volcanologists monitor the sulfur dioxide to gauge the activity of volcanoes.SHANE CRONIN: This is the telescope. And it’s a rotating one.NARRATOR: The more sulfur dioxide Shane detects, the more active the volcano.SHANE CRONIN: It’s going to be scanning over there, and I want it to scan above the level of the opposite caldera rim. We’re capturing it beautifully with this angle.NARRATOR: Shane’s readings indicate the satellites have been dangerously underestimating the levels of sulfur dioxide. Tofua is releasing far more than previously thought. Taaniela’s expert flying reveals that the magma has welled up in the crater, creating a lava lake, one of fewer than 10 on the entire planet. And there’s a sign Tofua has been actively throwing out lava, incredibly recently.SHANE CRONIN: This erupted in the last few days. It’s a fresh volcanic bomb. So, this really contrasts to all of the rest of the older material around here. So, there’s been some quite big explosions to produce these. It’s really interesting, because it looks as if Tofua is entering a new phase of activity, one that we haven’t seen here before. Everything that we’ve discovered today is absolutely new and, I think, will be of quite a shock around the globe.

Volcanologists visit Tofua to study the volcano’s activity.

Witnesses Recount Surviving a Volcanic Explosion

Hear witnesses share how they survived the most explosive event ever recorded on Earth.
At 5:15pm on January 15, 2022, satellites recorded the volcano Hunga Tonga-Hunga Ha’apai blast a cloud of ash and rocks into the atmosphere. Within minutes, tsunami waves crashed into the South Pacific nation of Tonga. These are the stories of some of the survivors.
Witnesses Recount Surviving a Volcanic Explosion Published May 10, 2023Branko Sugar: We were going spearfishing, just like we do now, me, my son and the boys. We could see it from here. It was nothing out of the ordinary. And then we see the mushroom was kind of getting bigger.Branko Sugar’s son: Look, look. It’s happening in a couple of minutes.Passenger: It’s spreading. Wow.Branko Sugar: And suddenly, the explosions came. I knew what was coming: tsunami.I accepted the fact that we have three minutes left to live. I just felt sorry for the boys, my son and the other boys. They were busy taking pictures and laughing, but I knew, you get hit by tsunami, you go to deep water. Just go. But the wave is chasing us and coming fast. Now, we are in the deep water. We can see the wave come to the other side and hit the main island. It must have gone underneath us. We didn’t even feel it.We thought we were now okay. Just go home, and that’s it. But the worst was to come. It starts to rain rocks on us. And then everything went pitch black. You couldn’t see your hand in front of you. Everything was dark. No electricity on the island. No electricity, no lights. Three hours, fighting to see.Narrator: Branko and his family had survived the most explosive event ever recorded on Earth. At 5:15 p.m., on January 15th, 2022, satellites witnessed the volcano, Hunga Tonga-Hunga Ha’apai blast a cloud of ash and rocks up into the atmosphere. Within minutes, tsunami waves crashed into the South Pacific nation of Tonga.Naomi ‘Emelio: I ran with my son. I could see that the wave was higher than this house.Salote Kafoa: We saw a huge wave. At first, it came splashing over the top of the church and school roofs.‘Ana ‘Akau’ola: A boy came and reached out to grab me. I said, “What are you doing?” He said, “I am going to carry you, so we can escape.”Narrator: Rock and debris rained down on Tonga for over 10 hours, covering the country in a layer of volcanic dust.

Hear witnesses share how they survived the most explosive event ever recorded on Earth.

A landscape photo of the Cap Cod beach ecosystem where students walk in a single file line between the dunes.

Students in Nancy Gifford’s 7th grade science class participate in an annual field trip to Cape Cod National Seashore where they spend the day investigating sea-level rise, salt marsh carbon sequestration, and the changing diversity of species found in New England. Image Credit: Nancy Gifford

How to create local climate change projects with your students

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The mounting impacts of climate change are perhaps the greatest challenge facing our society in the next century. From heat waves and megafires to droughts and more intense storms, the United States is already experiencing a range of effects. At the same time, <a href="https://www.pbs.org/wgbh/nova/video/weathering-the-future/">innovative solutions</a> have emerged which draw on new and ancient wisdom as communities across the country are learning how to adapt. In U.S. schools, many teachers are increasingly being confronted with conversations about climate change by their students.According to a <a href="https://www.edweek.org/teaching-learning/teens-know-climate-change-is-real-they-want-schools-to-teach-more-about-it/2022/11">nationwide survey of teenagers by EdWeek Research Center</a>, 79% of high school students believe that climate change is real, and that it is mainly caused by human activity. However, the survey also found that just because students believe that human activity is driving climate change doesn’t mean they fully grasp the science behind it. Furthermore, 76% of teachers <a href="https://www.edweek.org/teaching-learning/students-want-climate-change-education-most-teachers-dont-get-enough-training/2023/01">have not received any professional training or education</a> on how to teach climate change — which affects their ability to accurately convey the scope of the problem and solutions.The United States has not mandated or developed nationwide teaching standards for climate change science in secondary schools. But for teachers who are invested in teaching it, designing <a href="https://link.springer.com/chapter/10.1007/978-3-030-32898-6_5">inquiry-based projects</a> about local impacts and solutions can provide an entry point for students to conceptualize climate change concepts.NOVA interviewed three secondary school science teachers who have done this. Here’s how they are creating meaningful learning experiences, and how to apply their best practices to your own classrooms.
<h3>Provide opportunities for students to observe local impacts</h3>
 For Nancy Gifford, a 7th grade science educator in Chatham, Massachusetts, having students observe local climate change impacts helped bridge the gap between the disciplinary content and the real-world implications. One of Gifford’s favorite projects is a field trip to Cape Cod National Seashore that involves local park rangers and experts from the <a href="https://coastalstudies.org/">Center for Coastal Studies</a>. Gifford has been leading this field trip for the past eight years and over the course of the day students break into groups to do hands-on projects. They assess sea-level rise on Eastham Beach by measuring how the shoreline has evolved over time and where it is expected to be in 10-20 years; they collect core samples of marsh sediment to examine carbon sequestration in the marshes; and participate in a fishing activity to explore the changing diversity of species found in New England.“They're finding a lot of southern species moving up into the Cape Cod National Seashore area, and they're also noticing that the lobsters are moving further north,” Gifford says. “So now you don't really find lobsters south of Cape Cod anymore because of where the water is warming due to climate change.”When it comes to understanding how climate change is affecting the fisheries, every student knows someone who might be impacted directly or indirectly, Gifford explains.“They're either serving it on a plate or they're cooking it, or they're actually catching it and processing it,” she says. “That knowledge catches some of the kids that may not have been as interested at first about why this matters, but when you can show them climate change in their backyard, it makes it more real.”While a field trip to Cape Cod National Seashore is not accessible for every class, Gifford encourages educators to reach out to local naturalists and research centers to plan experiences. She also recommends using climate data from national research organizations or science outlets like <a href="https://climate.nasa.gov/">NASA</a>, <a href="https://www.noaa.gov/education/resource-collections">NOAA</a>, <a href="https://www.need.org/resources/climate-science-materials/">The NEED Project</a>, <a href="https://www.theclimateinitiative.org/">The Climate Initiative</a>, and <a href="https://ny.pbslearningmedia.org/collection/nova/t/earth-space-sciences/earth-human-activity/">NOVA</a> to help complement lessons.
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<h3>Transition from personal accountability to collective commitment</h3>
 In Tucson, Arizona, earth science and chemistry teacher Erik Fleming has found that one of the easiest climate resilience concepts for students to connect with is water conservation and usage. Fleming has students start by analyzing their family water bill. On the bill students are able to see things like household water use and how it compares with local water use averages on a graph. Within their household they calculate each individual’s usage and then create a personal plan to save more water.“This is the third time I've run this project with students and they've dialed it in really well,” Fleming says. “They have a good understanding of their own uses and personal contributions, and I try not to deflate them at the end, but they do figure out that they're probably much better at this than they think they are just by virtue of growing up in a desert.”In the 1970s, the city of Tucson was largely dependent on groundwater, but was <a href="https://www.kold.com/story/25862392/tucson-water-hits-a-milestone/">struggling to keep up</a> with the demand of a growing population. One of the water security tactics the city employed was transitioning to a <a href="https://waterinthewest.stanford.edu/news-events/news-press-releases/pricing-water-conservation-using-tiered-water-rates-structures-qa#:~:text=The%20lowest%20price%20block%20or,large%20lawns%20and%20swimming%20pools.">tiered water system</a>, in which customers could consume the amount of water necessary for needs such as for drinking and bathing at a lower price, but paid more as water usage exceeded essential needs, making things like maintaining lawns and swimming pools more expensive.“The city water department has been very proactive about education and outreach and also getting people to do more natural landscaping and less swimming pools,” Fleming says. “Because of this kind of community emphasis, to get students to the next level we calculate the entire watershed's water budget, and it does turn out that the city of Tucson and the Tucson Basin use less water than falls from the sky.”While Tucson is part of the Sonoran Desert ecosystem, the city can experience higher rainfall in the summer months, particularly August. During this time the city is inundated with several inches of rain.“We can get a couple of inches of rain in a day, which is intense for Tucson, and there's nowhere for it to go,” Fleming says. “So the long-term plan, after students understand their personal water use, is actually figuring out how we can redesign built infrastructure to better manage the flow of water.”
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<img alt="Three male students are filling in groundwater withdrawals diagrams in Erik Fleming's class." class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Erik_Fleming_Students.width-990.png"/>
<figcaption>Following the water bill assignment, students in Erik Fleming's earth science class examine groundwater withdrawals to learn about responsible urban growth. Image Credit: Erik Fleming
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<h3>Encourage collaboration across scientific disciplines and state lines</h3>
 For the past 22 years, George Hademenos has been teaching high school physics in Richardson, Texas. “I don't like to just come in and address curricular objectives. What I want to do is make those objectives come to life for my students,” Hademenos says. “Climate change is a serious scientific issue and I want kids to be able to understand what it is, what it means, and how it impacts them.”This dedication to student excellence is what earned Hademenos an engineering education award at the 2023 National Science Teaching Association’s national conference in Atlanta.For Hademenos, climate change has always been an integral component of his physics curriculum to illustrate real-world extensions of concepts taught in class.High school physics students primarily learn about <a href="https://www.nextgenscience.org/sites/default/files/HS%20PS%20topics%20combined%206.12.13.pdf">core concepts</a> such as waves and electromagnetic radiation, energy transfer, forces and interactions, and structure and properties of matter. Hademenos builds on these existing standards by challenging students to apply that knowledge to complex, interdisciplinary problems like climate change.In one project several years ago, students designed, modeled, constructed, tested, and analyzed data from a 3D-printed rover vehicle referred to as <a href="https://aapt.scitation.org/doi/abs/10.1119/1.5084920?journalCode=pte">ROAVEE (Remotely Operated Amphibious Vehicle for Environmental Exploration)</a>. The rover was equipped with sensors to collect data from air and water as the vehicle navigated on solid terrain as well as on water.“Physics is hands-on science. It's not really something to be taught, it's something to be explored with your hands,” Hademenos says. “The overall objective of this project was to work in collaboration with another teacher so that we could do the mechanics part and then we could give it to the AP environmental students who could then use it to get more detailed data.” This year, Hademenos participated in “<a href="https://www.floatboat.org/?fbclid=IwAR3CATWuTYQg87PwX9tjIiheVOYp8-Qx3SzGhoeSFrScDr40AL1Sre2VTCA">Float Your Boat</a>,” a project coordinated by the University of Washington Polar Science Center. It allows students to participate in ongoing research and learn about the circulation of the Arctic Ocean and how its sea-ice cover is changing.
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<img alt="In the Arctic tundra two polar scientists hold up signs for Richardson High School and Shaler Area Elementary and Middle Schools" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Float_Your_BoatRichardson_High_School.width-990.png"/>
<figcaption>Physics students from Richardson High School participated in "Float Your Boat," an international project designed to engage students in polar science, as well as the impact of climate change on polar regions. Image Credit: Sarah Johnson, Ignatius Rigor, and Jim Johnson
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Hademenos’s students decorated 8-inch long wooden boats, each stamped with a number and a web address provided by the Polar Science Center. These boats are then transported to the Arctic Ocean and embedded on an ice floe with a buoy. The buoy will transmit location data and the students can log into a website and track their boats throughout the process.The students will also be communicating with a high school in Utqiagvik—the northernmost town in Alaska—who are working on the same research project to foster collaboration.For Gifford, Fleming, and Hademenos, it’s not enough to just address climate change in the classroom. They strive to help students connect with impacts and solutions in their communities in a variety of ways.“I think when (students) go back to their own beaches, they're seeing that the tides are higher in their neighborhoods,” Gifford says of the students who have participated in the Cape Cod trip. “Areas that are flooding that would only flood during a hurricane or big storm are flooding pretty regularly now, and I think that that probably has the most impact on them because it's real, and they can see it, and we can measure it.”
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Three STEM educators share best practices for tackling climate change in the classroom through project-based learning.

An up close underwater photo of a lionfish swimming towards the camera with its mouth open

Lionfish Invasion | Ocean Invaders

Learn how the lionfish has disrupted ecosystems of the Atlantic Ocean in this video from NOVA: Ocean Invaders. Use this resource to highlight how the introduction of an invasive species can lead to changes that disrupt an entire ecosystem and threaten the survival of other species.

An aerial visual of the MOSE flood barrier gates being raised out of the water

Considering the Trade-Offs of Strategies for Protecting Venice from Flooding | Saving Venice

Learn about strategies that engineers are designing to meet the challenge of rising flood waters in Venice in this episode from NOVA: Saving Venice. Use this resource to illustrate the trade-offs of different design solutions and the benefits of multiple strategies when trying to solve a complex problem.

People in Venice walking through flooded streets in rain boots and rain gear

How Earth’s Systems Interact to Affect Flooding in Venice | Saving Venice

Learn how Earth’s systems interact to contribute to Venice’s flooding problem in this episode from NOVA: Saving Venice. Use this resource as an example of how scientists employ data to help protect a community from natural hazards.

Topic: Planet Earth

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