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Season Three, Episode 3: On the Surface

Season 1Episode 3Nov 3, 2020

Like waves of the ocean, our planet’s surface is in constant motion. In this episode, we’ll travel to tropical rainforests to dig into soils with an ecologist, and fly drones with an earthquake expert to spot shifts in the ground beneath our feet.

On a mission logo

On a mission logo


(sound FX: Costa Rica jungle)

[0:03] Narrator: Earlier this year, a team of scientists trekked through the dense jungle of northwest Costa Rica, where active volcanoes loom over the landscape. Josh Fisher, a JPL ecologist, led the expedition.

Josh Fisher:I work on terrestrial ecosystems — anything to do with plants, soils, water, nutrients, carbon.

Narrator: He was seeking to answer a question about carbon dioxide, or CO2, that’s been bugging him for years.

(sound FX: mosquito and slap)

[0:36] Josh Fisher:The biggest uncertainty in the Earth system and projections of Earth’s climate, when it comes to the land component, is how much CO2 will tropical ecosystems absorb in the future? They’re what we call the lungs of the planet. We just don’t know how much of all our emissions they’re going to be able to breathe in.

So what we’ve done to answer that question thus far is set up CO2 experiments. We shoot CO2 out of pipes onto forest, and they’re really difficult to set up, real expensive. We set up these pipes — these rings that surround a dozen trees or so — and you’ve got to pipe in the CO2, and then you measure how much CO2 the plants take up.

[1:22] But these experiments are not in the tropics. If you go to your backyard in Tennessee or Massachusetts, there’s only so many species of trees, and you could count them on your hand sometimes. But when you go to the middle of the Amazon rainforest and you walk for five minutes, you’ve just seen ten times the amount of species as there are in all of England. So it’s nearly logistically impossible to take the measurements in these jungles, across the amount of tree species required to say anything about the ecosystem as a whole, across the timescales that we’re interested in climatically.

So we’ve been stuck. We’ve been stuck at this critical barrier for one of the most important scientific questions of our time.

Narrator:But then, a fortunate encounter gave Josh hope that he could finally cross this barrier.

[2:13] Josh Fisher:I had a colleague at JPL, Florian Schwandner, and he’s a volcanologist. And he got put in my group in a reorganization at JPL. And so Florian was hearing us talk about this problem about how we don’t have elevated CO2 experiments in the tropics. And he said, “Did you know that the number one dry gas that comes out of volcanoes is CO2?”

And I really didn’t know anything about volcanoes at the time. I said, “Oh, really? But is it out of the crater where all the lava comes out?” He said, “Oh no, not just out of the crater, but it comes out of these cracks and fissures way beyond the volcano. The volcanic complex underground goes for miles beyond the crater that you don’t even see, where all the forests are. And CO2 is the only thing that really comes out.”

And so, we surveyed all the volcanoes in tropical areas. And there happens to be a chain of volcanoes in Costa Rica that are surrounded by pristine rainforest that span extremely wet rainforest to a little bit more-drier rainforest; kind of every flavor of rainforest you can imagine across the world. And the volcanoes are different ages. So the CO2 has been coming out in different lengths of time. So as soon as a crack or fissure forms in the landscape, it could be a hundred years ago, a thousand years ago, whatever, CO2 just starts coming out. So instead of pipes that you had to set up and CO2 that you have to truck in, it’s just coming out, constantly.


[3:45] Narrator: Soils all over the world release carbon dioxide, even without volcanoes nearby. Just as you exhale carbon dioxide with every breath, so do many microorganisms like bacteria and fungi, and soil is full of these tiny forms of life. Since plants absorb CO2 to produce food, you’d think volcanoes adding even more of this gas would just mean more food for plants. But too much CO2 can actually acidify soils and kill off plants.

Volcanoes shape their environment in ways both subtle and obvious. A volcanic eruption can decimate the landscape in an instant, but recovery can happen quickly, thanks to minerals and other aspects of volcanic ash that enrich depleted soils. In fact, some of the most fertile soils in the world have volcanoes to thank for their bounty. As dangerous as it can be to live near an active volcano, humans have always weathered this risk because of the rich rewards.

To find out how the Costa Rican volcanoes are affecting the local soil and plants, over the next few years Josh and his colleagues plan to canvas the area by flying instruments on drones and airplanes, using satellite images and data that gather wide-scale measurements of forest health and growth, and of course, putting feet on the ground to make more detailed measurements.

[5:12] Josh Fisher:Mother Nature is providing this natural experiment, and so now we can go in to these ecosystems and say, “Well, how much CO2 did you absorb over the last hundred years at these higher rates?” And they will tell us how much CO2 we expect the rainforest to absorb over the next hundred years. You know, that’s a window into the future of the Earth, hidden in these jungles of the Costa Rica volcanoes, kind of this crystal ball.

(Intro music montage)

[6:15] Narrator: Welcome to “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory. I’m Leslie Mullen, and in this third season we’re traveling to the ends of the Earth with scientists who explore every aspect of our amazing world. This is episode 3: On the Surface.


Narrator: Earth – not the planet itself, but the soil, the “earth” that makes up the part of the planet we walk around on – is a lot more than meets the eye. Most soils are a world unto themselves, composed of a variety of rock types in many particle sizes, suffused throughout with air and water. Just like residents of a bustling city, communities of microorganisms and animals like worms and insects keep the soil vibrant — most notably by breaking down organic matter, like dead leaves and wood, liberating and recycling the elements trapped within.

In our planet’s earliest days, all life was in the sea. The landscape was a wasteland of cooled volcanic lava, as barren as the Moon. How did we go from that desolation, to the diverse ecosystems of today?

[7:32] Josh Fisher:Imagine the first land. There’s no soil, it’s just a bunch of rock, this lava that hardened. And then, the rock itself starts to break from rainfall and waves crashing into it, and so on. So how do you grow anything there? At first there will be some plants that will cling to those rocks, and get the rainfall and the sunlight for photosynthesis, but where are they getting the nutrients? Land plants need a bunch of nutrients, especially nitrogen and phosphorus.

So a lot of that rock might contain phosphorus, but what about the nitrogen? There’s a lot of nitrogen in the atmosphere, and not all plants can use it. But some plants have bacteria that they house in a symbiotic relationship on their roots. And so the plants will photosynthesize and make sugar, and pay it to their subletting bacteria. And those bacteria use that energy and they grab that nitrogen out of the air, and give it back to the plants as a nutrient. So that’s how those nitrogen-fixing plants can survive on a rock with no nitrogen.

So then, they’ve got a bunch of nitrogen in their leaves and wood and so on. And those leaves fall and the leaves eventually decay into something that looks kind of like soil. And so now you’ve got soil that only not only has phosphorus, but now has nitrogen. Over time you can build up an ecosystem of soil that is nutrient rich, and a diversity of different types of plants can grow.

[9:06] Narrator:Every time life devised a way to enter new territory or make use of a new resource, that would lead to changes in the landscape. Sometimes these changes would encourage more growth, but what makes one area lush and another barren depends on many factors.

Josh Fisher:There’s all these fertile areas where the soil and water and climate interact to create great growing conditions for agriculture. There’s the Nile River Delta, the early breadbasket; the Ganges in India. I’m sitting here in California; we have the Central Valley of California that grows a lot of food. It used to be an inland sea, and it ended up being very fertile, and there’s a lot of water that comes off in the adjacent mountains. But if it weren’t for the water that was diverted into these areas, they wouldn’t be as fertile. They’d just be grasslands. So it’s that combination of nutrients as well as climate.

(sound FX wind and rain)

I think that the Sahara Desert actually has some decent fertility, but of course, there’s no water there. Another interesting thing about the Sahara Desert is that it’s very obviously dusty, sandy there, and the wind blows that dust, that Sahara top surface off into the air, and it lands on the Amazon, which actually is a little bit poor in some nutrients, especially phosphorus. Remember that phosphorus comes from the rock, and that rock gets broken away through rain. And as you know, in the Amazon rainforest, there’s a lot of rain. So you can imagine a lot of that phosphorus rock has been broken down from all that heavy rain and has leached out to the ocean, making the Amazon basin a little bit depleted of some nutrients like phosphorus. So you end up getting this phosphorus delivery from the Sahara that helps grow the Amazon rainforest.

[10:50] Narrator:Sometimes it’s not so apparent why one area is more fertile than another, or why a farm that once was productive suddenly isn’t doing well. That’s where NASA missions can shed some light. Josh is the Science Lead for ECOSTRESS, an instrument on the International Space Station.

Josh Fisher:What ECOSTRESS actually detects is the surface temperature of the plants. If the plants are heating up, it’s because they don’t have enough water. Plants sweat, like us. When they’re using water, they cool themselves down. That’s what ECOSTRESS gets after is kind of the plants’ sweat. So we can use that direct temperature measurement to get at the actual water use and stress.

With ECOSTRESS, we work with agriculturalists a lot. We have US Department of Agricultural Science members on the science team. And they’re using ECOSTRESS for all sorts of interesting science questions, as well as societal applications. One example would be if USDA is trying to help farmers figure out which variety of lettuce to grow, they might run some sort of an experiment where they grow different varieties of lettuce, and they want to know how much water each one needs. And so ECOSTRESS can help tell them that. And then they can put out their recommendations to their farmers in areas that don’t necessarily have a lot of water.

[12:13] ECOSTRESS was one of the first missions to use the Space Station as a platform to investigate questions of the Earth. And we kind of paved the way for other missions also looking at ecosystems. There’s a mission called OCO-3, also on the Space Station, which looks at plant fluorescence, or plants glowing from photosynthesis.

So light is used for photosynthesis. Plants absorb red and blue light especially. But some of that light gets bent and re-emitted in a slightly different part of the electromagnetic spectrum. That’s what we’re calling the glow, essentially, is this fluorescence, light that gets bent through photosynthesis. And what’s nice about the fluorescent light is that we can see it from space, and so that allows us to track it globally. And it gives us direct insight into the photosynthetic machinery and activity of plants. Without that, we really don’t know if plants are photosynthesizing.

And that’s important because, it’s like if you were to go to your doctor, and your doctor didn’t know if you were sick until you were dead. We didn’t know if plants were not photosynthesizing until they lost their leaves. Now with fluorescence, we can see that photosynthesis shutting down before they lost their leaves, and that enables land managers to potentially take action.

[13:36] Narrator:The ECOSTRESS and OCO-3 instruments are complemented by other Earth-focused instruments on the Space Station, like the German Space Agency’s DESIS instrument, which can identify the chemistry and geology of different regions, and NASA’s GEDI, which uses lasers (sound FX: Star Wars lightsaber) — not to battle Sith Lords, but to make 3-D images of forests. Josh also works on a mission called SMAP, a satellite that measures soil moisture.

There isn’t one big instrument to study all the aspects of Earth, because each type of measurement requires special tools and techniques. It’s kind of like different musicians in an orchestra playing a symphony together, or an artist using different colors and brush strokes in a painting.

(music: Mozart Piano Concerto No.21, K647)

Josh Fisher:So now you’ve got missions that are measuring the three components of ecosystems, what we call structure, composition, and function. And you really need to be able to know all three of those to understand an ecosystem. It’s kind of like an RGB lens, right? You can’t just view the world in red or green or blue, but when you bring them together, you get the true color. And so in order to really understand ecosystems as a whole, or the Earth as a whole, you do need to connect all the different measurements together.

[15:01] Narrator: Satellites and Space Station instruments can’t give us a complete picture of Earth. They can provide an overview of a region, but at their great distances, orbiting so high up, their eyesight isn’t good enough to see the finest details. And they can be rendered essentially blind over areas often covered in thick clouds, like the tropics. To see more, scientists must venture into some of the most remote regions on the planet.

Long before Josh’s excursion to the Costa Rican rainforest, as a researcher at Oxford University he spent four years in the Amazon jungle and the Andes mountains of Peru, studying the abundance of nitrogen and phosphorus in the soil, and also fertilizing trees with these elements to see how they’d react.

Josh Fisher:When I was working in the Amazon, we would have to trek with all our stuff on our backs for days to get to some of the sites across rivers. We’d have no roads, or the roads had been wiped out from either landslides on the Andean face or rains or whatever, they’re all just dirt, and not very good infrastructure in Peru at the time.

So we’d have our tents and our cookware, as well as all our water and bags of fertilizer, and we’d be carrying back bags of soil, all on our backs. And in the jungle there might be snakes and spiders and, In some parts, there were these bears.

[16:26] Narrator: All the trips had their difficulties, but one stands out from the rest.

Josh Fisher:We were on the Andean slope, so we were halfway between the top of the Andes and the bottom, in the Amazon area. And it rained that night, and it was wet and we’re sleeping not on flat surfaces, and on hard surfaces too, which is not very comfortable. And in the middle of the night we heard a rattle and we weren’t sure what it was.

(sound FX rustle/rattle noises)

Josh Fisher:The trail we were on was potentially used by drug runners. And there’s this house at the very top of the Andes where a woman had murdered her husband, and it was famous for that. And there were these other stories that we’d like to tell around the fire about these ghosts or these legendary stories. And so we heard this rattle at night and we were like, “What was that?”

(rattle music)

[17:15] Narrator: Hoping the element of surprise might scare off whoever was disturbing their camp, they quietly coordinated a defense.

Josh Fisher:One of the tents murmured a very low “uno.” And then after that, a few moments later, there was a little bit of a louder, “dos.” We basically at that point knew we were doing a countdown. And then a few moments later there was the, “TRES!” and we all yelled it out, and turned on our flashlights at the same time, threw off our tents, and yelled with our knives out, and they ran off into the forest.

Narrator: Because it was so dark and disorientating, with flashlight beams bouncing all around the trees and creating strange shadows, no one could quite see who the intruder had been. But the next morning they saw bear tracks, and found a few scraps of their remaining food strewn about the forest floor.

Without food, they couldn’t continue their work. Their group of ten was composed of two teams that had different needs for their science projects, so they decided to split up — one team would head uphill to a base camp in the mountains, and the other would go down, deeper into the Amazon forest.

[18:33] Josh Fisher:I was on the team going into the Amazon ’cause we needed more data farther on, and we would just rendezvous at the base camp down below. And we knew we had to get moving, ’cause it takes a day to get out, and we had already spent the morning just dealing with packing up.

(sound FX rustles and walking in forest)

A few hours into it, we did a water check, and each of the people in my team thought the other had all the water, and we realized that none of us had the water. And that the other team had taken all the water. So things became pretty critical at that point. You have no food, no water. You got to move while you still have the calories and the water in you. You had to get there in a day, right? You couldn’t do it in two days, because you’re already dehydrated at that point. We knew that, based on our timing of when we started, we would hit nightfall. And that’s when it would become extremely dangerous, because in the middle of the jungle, it’s hard to see these paths.

(sound FX walking in swamp)

[19:33] We were crawling with all our junk on our backs through mud swamps, and some of the path goes under the forest. We had to crawl through tunnels underneath the forest floors, because these tunnels were carved out by streams and whatnot. You could actually see the roots from the trees above sticking into these tunnels, and they get snagged on our packs and scratch our faces.

Then night fell, and we weren’t completely sure that we were on the right path.


Narrator:They were struggling through the dark forest primeval for endless hours, tired and sore, hungry and thirsty, the trees reaching out with stiff clawed fingers that drew blood as they dug in and threatened to never let them go.

(sound FX branches breaking and whispers)

Narrator:But then, at the witching hour, they made their escape.

[20:29] Josh Fisher:In the very middle of the night, we popped out onto the main road. We were really happy. We hooted and hollered; we kissed the ground. But we weren’t out of it yet. We had to keep going another hour or so down the road. But we were walking like Zombies.

(sound FX Zombie)

Josh Fisher:At one point, me and one of the guys I was walking with sat down to take a brief rest, but we both passed out in the middle of the road. That wasn’t the safest place to take a little nap, and I was woken up by his snoring.

(sound FX Zombie)

Narrator:The teammates had spread apart as they’d staggered down the road, but they soon were together again, their passage to the base camp blocked by a deadly foe.

Josh Fisher:We had all stopped because in the middle of the road, one of the most dangerous snakes in the region was sitting there, ready to attack us. And so we were just like, seriously? Like, after all of this?

Narrator:They passed this final trial in their journey not by answering the riddle of the Sphinx, but by yelling and throwing rocks, scaring the snake away.

[21:35] Josh Fisher:Just around the corner from the snake on the road, to our amazement was a waterfall.

(sound FX waterfall)

Josh Fisher:And we were really dehydrated at that point and disgusting from crawling through mud swamps. So we hollered for joy and stripped off like everything, and jumped in and just drank. And we were pretty much revitalized at that point.

Narrator:Grateful to be alive, they finally made it to the base camp, which was just a simple wooden shack. But it had snack food and water, and it was a dry place to roll out a sleeping bag and sleep. Although they were on a tight schedule and had many more soil samples to collect, they took a day off to recover from their ordeal.

Josh Fisher:We just listened to music and we went back up to the waterfall and ate a lot of oranges and cookies. And then the next day we set off to the next site and went back into the jungle again.

(sound FX jungle)

[22:34] Narrator:The soil that nourishes plants represents a tiny fraction of the rock that makes up our planet. Between Earth’s top crust and the metal core is an enormous realm known as the mantle. The mantle gets hotter the deeper you go. The upper rocks of the mantle are more solid, and as you get closer to the core, they become more liquid.

One way to study this deep structure of Earth is to start digging.

Movie trailer excerpt: Journey to the Center of the Earth (2008)
For centuries there has been a legend of a land untouched by time. Explorers have vanished searching for it. And now one man will set out to discover the truth…

Trevor Anderson:A Journey to the Center of the Earth. It wasn’t just science fiction.”

[23:23] Narrator:We know the inside of Earth is nothing like Jules Verne’s novel, “Journey to the Center of the Earth,” or what was depicted in the many movie adaptations. But this is a hard region to study.

The deepest hole in the world is the Kola Superdeep Borehole in Russia. That hole is just 23 centimeters across, but goes down over 12 kilometers, or seven-and-a-half miles. It took the scientists 20 years to reach that depth, and the temperatures of around 180 degrees Celsius, or 356 Fahrenheit, were twice as hot as they’d expected.

Their goal wasn’t to dig to the center of the Earth, instead they wanted to reach the boundary layer between the crust and the mantle so they could learn more about it. But the project had to be abandoned after only having made it a third of the way down through that portion of the crust.

A few other groups have tried to reach that crust/mantle boundary, but also without success. The Dutch artist Lotte Geeven was curious what you’d hear at the bottom of one of these super-deep boreholes, and so she lowered a thermally-shielded microphone down one that’s in Germany.

(sound effect: “The Sound of the Earth,” Lotte Geeven)

[24:45] Narrator:Scientists who study earthquakes are well-acquainted with our planet’s rumblings. The unsettling vibrations of earthquakes occur when segments of the crust, called tectonic plates, slide around on convective heat currents in the mantle. Sometimes one plates dives underneath another, sometimes they collide. This is how mountains and volcanoes are made; this is what pushes the continents closer together or farther apart.

Scientists don’t know precisely how or when plate tectonics started on our planet – estimates hover around 3 billion years ago — but one benefit is that it keeps essential elements like carbon, phosphorus and calcium moving around the planet, free for life to use, rather than bound up in the rocks forever. Tectonics help drive a cycle of rocks being broken down, compressed, melted, and cooled – over and over again. Like waves of the ocean, our planet’s surface is in constant motion.

Andrea Donnellan is a JPL geophysicist who studies earthquake faults, which are deep fractures in the crust.

[25:56] Andrea Donnellan:Where the tectonic plates grind together is where they have earthquakes. So they’re a little bit stretchy and elastic, and they stick for a while until they exceed some stress, and then they break, and that’s the earthquake that we feel.

And then the Earth is much more complicated, and it’s got soft spots and compliant parts and preexisting faults. And so those all respond after the earthquake occurs in different ways. And that’s what I study: how does the Earth stretch and break and respond, and how do stresses re-adjust following earthquakes?

So I’m using data from airborne radar that JPL flies, developed under NASA. I fly drones, or small uninhabited aerial vehicles, to study the near surface around faults and earthquake ruptures. And I use Global Navigation Satellite System to understand how the Earth’s crust deforms.

[26:52] Narrator:Before that technology came along, she would set up tectonic-monitoring GPS stations, and then gather earthquake data from each of them. But that method had some problems.

Andrea Donnellan:We only were able to collect data about every six months, so we didn’t have a good continuous time series. The stations, especially after an earthquake, were difficult to get to. In 1994, the magnitude 6.7 Northridge earthquake occurred.

NBC-LA news broadcast, 1994 Ridgecrest earthquake
We’re here in the Channel 4 newsroom as you folks, there’s no surprise for any of you folks this morning, we’ve been hit with a major earthquake. Right now we’re trying to basically gather some more information trying to figure out where this has been centered. I’m not sure if we can take a look around for that right now. But half the newsroom behind me has been disheveled a lot, and television monitors knocked off the shelves, basically a lot of dust kicking around here. We’re trying to figure out again where the earthquake has been centered. It hit about 4:34 this morning, a very sharp jolt, a very long, a very rolling type of motion…

[27:49] Andrea Donnellan:After the Northridge earthquake, when I drove in the field, I came upon the Balboa gas line and water line breaks. So there was a big fire, so we had to go around that. And then we tried to go up on the mountain where we had a station, and there were landslides and boulders in the road. And we had to clear all that to get up into the site.

So it was not efficient, and we couldn’t see change easily in time, either before or after the earthquake. And that’s what spurred the development of these continuous GPS networks that we now rely on.

Narrator:Compared to the large-scale surveys made by space satellites, Andrea’s drone flights can spot more details over smaller areas.

(sound FX: Parrot Anafi drone)

[28:32] Andrea Donnellan:The drones I fly are tiny. They’re about eight inches long. They don’t weigh very much, but they have very good cameras on them, and get high resolution detail on the order of one to two centimeters. Typically we fly in a 500 by 500 meter area, or a quarter mile to half mile wide area. It’s automated, and It flies a grid pattern, a double grid, so it flies a grid in one direction, and then across in the other direction.

(sound FX: Parrot Anafi drone)

Andrea Donnellan:When we do field work, there’s a lot of prep work the day before. We have to notify people that we’re flying, we have to notify the FAA that we’re flying. We have to charge all of our batteries. There’s always firmware updates to be done; there’s computers to charge.

Then once we do that, we get up very early and drive out in the field. And then we set up a GPS base station, and we have a real time kinematic rover station. And that we use to survey the ground control points. So we put these targets on the ground that we can image from the air with a drone so that we can precisely adjust our images to be very accurate.

[29:41] And then we fly the drone. So we have a pilot — somebody who operates the autonomous drone control software — and then an observer who also is a second pair of eyes on the drone. And then we download all those data in the field to make sure we actually collected them. And then when we come home, we process them so that we get a very nice image and topography of that area.

Narrator:Andrea has been to some of the most isolated parts of the world, like the salt flats of Bolivia and the steppes of Mongolia, studying different aspects of the Earth’s crust. She’s been to Antarctica seven times to study the ice, tectonics, and post-glacial rebound. One effect of massive glaciers melting is that it causes the Earth’s crust to slowly bounce up — like what happens when you get up off a mattress – and that can cause earthquakes unrelated to plate tectonics.

But now Andrea’s main fascination is with the earthquakes of Southern California, and how they’re triggered by different kinds of action.

[30:45] Andrea Donnellan:It’s a nice, sweet spot — between the complexity of the plate tectonics; we have a spreading center in the Gulf of California; we have compression here in the San Gabriel Mountains and the Transverse Ranges; we have shear from strike-slip motion from the Pacific North American plates. And then it’s extremely well instrumented. And so it’s a great opportunity to get a lot of insight into what’s happening at depth in the Earth.

Narrator:Despite all the instruments, satellites, and scientists keeping vigil over Earth’s many fault lines, it’s not possible to predict earthquakes.

[31:19] Andrea Donnellan:Earthquakes appear to pop off somewhat randomly. But we know the rate of plate tectonic motion and we can estimate the number of earthquakes that we should have. But where specifically they occur, or how big each individual earthquake will be, we don’t know that well.

So we don’t do earthquake prediction. We can establish probabilities that earthquakes will occur over some timeframe. So typically it’s been 30 years — that’s partly driven by the length of a typical mortgage on a house for the insurance industry. But earthquake forecasts are getting a little bit shorter. We’re able to do probabilities on five- to 10-year timescales, but these are over regions that are fairly large, like Southern California. But we can also estimate which faults are more active and maybe more likely to have earthquakes on them.

We can see where strain is higher or lower on faults, and one of the things we’re trying to get at right now is, what do these measurements mean? How do we know where an area’s going to break in the future, versus where it broke the past? The Parkfield segment of the San Andreas fault, for example, ruptures in the same place almost every time, but in other places they don’t. And often earthquakes happen where faults are either not mapped, or not expected to produce an earthquake.

[32:41] Narrator:If you look at a map of earthquake fault lines, you’ll see what appear to be scores of haphazard and overlapping scratches. Most faults can’t be seen from the surface because they’re just too far underground. Not all of these deep scars in the skin of our planet are forever; over time some of these faults actually become healed.

Andrea Donnellan:So what can heal a fault? Mostly pressure — confining pressure from being in the Earth. Water activity can move in the faults; I would think that probably often maybe weakens the fault. We don’t really know, it could crystallize material, which strengthens the fault as well. So when an earthquake happens, is that section of the fault weaker now, or does it heal so that it’s just the same as the surrounding material?

Narrator:The effects of earthquakes often go beyond fault-shifting and ground-shaking.

[33:33] Andrea Donnellan:Earthquakes can damage critical infrastructure, not just buildings, but pipelines. So they can cause wildfires. So one scenario could be you have an earthquake that causes a wildfire. The earthquakes also loosen the land, the wildfires further degrade the surface of the earth; the trees aren’t holding the land. And then when you have heavy rains later, you’ll have the debris flows. So they’re all connected.

Narrator:Earthquakes that happen near coastlines or on the ocean floor also can generate huge tsunamis, with waves 100 feet high. NASA helps create hazard maps that estimate where the cascading effects of earthquakes could lead to wide-scale damage, and they coordinate emergency response scenarios with FEMA and other agencies.

2020 earthquake news reports:
ABC news reporter:
We’re going to begin with the chaos in Puerto Rico, a 6.4 earthquake and multiple aftershocks rocking the island just a day after a 5.8 earthquake destroyed multiple…
KCRA news reporter:…county where there’s been a pretty strong earthquake. 5.8 magnitude quake hit after 10:30 this morning out of the town of Lone Pine. The quake was followed by about a dozen smaller aftershocks, but so far there are no reports of any serious injury…
KREM news reporter:…tracking more than 40 aftershocks in southern Idaho. Most range in magnitudes 2 and 3. But this morning, a magnitude 4.1 aftershock hit around 5 a.m…

[34:52] Narrator:The magnitude numbers assigned to earthquakes and associated aftershocks refer to the amount of energy released by the events.


Narrator:In 1935, Caltech geologist Charles Richter created his famous “Richter scale” for earthquakes. But his scale specifically compared Southern California earthquakes, and so scientists these days instead use a more accurate “moment magnitude” scale to rank the relative power of earthquakes all around the world.

Every number up the moment magnitude scale represents about 30 times more energy released. Most people can’t feel magnitude 3 quakes or lower. The largest earthquake ever recorded was a 9.5, in Chile, sixty years ago. That quake lasted for 10 minutes, triggered massive tsunamis, killed thousands and left many thousands more injured or homeless.

[35:50] News footage: Valdivia, Chile earthquake, 1960
Chile pays the terrible human price it costs for the Earth itself to change its form suddenly. Rent by a series of shattering earthquakes, the land and its dwellings are crumbled and cracked. A sanctuary remains where a house of worship was partially spared, and a woman prays for lost family and friends. Nearly 5,000 are dead or missing in the disaster…

Narrator:As much as we’ve learned since then about earthquakes, the fact that we can’t predict them, and set up life-saving early warning systems, means we still have far to go.


Narrator:Andrea is part of one satellite mission, called NISAR, that’s scheduled to launch in 2022 and aims to better track changes throughout Earth’s systems, from melting ice sheets to erupting volcanoes to trembling earthquakes.

[36:41] Andrea Donnellan:So the NISAR mission is a global radar mission, joint with the Indian Space Agency that JPL is managing, that is like the airborne radar that I use, but it will be systematic and global. That will tell us a lot about earthquake processes.

And then, we’re working much more on developing high resolution topography technologies to understand what the land surface looks like and what it tells us about the past, as well as how it changes in response to earthquakes, volcanoes, landslides. So I think there’s a lot we’re going to continue to learn in the next 10 to 20 years.

Narrator: If you like this podcast, please subscribe, rate us on your podcast platform, and share us on social media. We’re “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory.

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