Nikki Gamble talks to science journalist and author Maya Wei-Haas about her recently published book, What A  Rock Can Reveal.

The discussion ranges from the creation of volcanic rock to stromatolites, the earliest known form of life on Earth. Maya also makes suggestions for engaging young readers with geology, no matter where they live.


Note: This transcript is edited for readability. Filler words are removed, and some sentences are reordered. The transcript remains faithful to what is said.

Nikki Gamble

Hello, everyone, and welcome to another episode of In the Reading Corner. I’m very excited today because I love talking to nonfiction authors, particularly people who know a lot about science. Today’s guest is Maya Wei-Hass. She is the author of What a Rock Can Reveal. Maya has a PhD in Earth Sciences. She has worked for Smithsonian Digital News and spent five years as a staff writer for National Geographic.

It’s lovely to have you here.

Maya Wei-Haas

Thanks so much for having me on.

Nikki Gamble

Before discussing the book, can you tell us a little about your background? What does having a PhD in earth sciences involve? Did you get to visit lots of interesting places?

Maya Wei-Haas

I did, actually. I discovered field work as an undergraduate. So, I did some field experiences and then did a program called Research Experience for Undergraduates. And went to Svalbard for the summer, which was amazing.

It was my first real opportunity to ask my own questions and figure out ways to come up with my own answers to those scientific questions. And then, I decided to continue research in this field. And so, for my PhD work, I did some work in Arctic Alaska and then Antarctica] as well. The reason for studying the Poles is that you can learn so much in these extremely sensitive environments. Many things that are difficult to detect when you are studying populated areas. My work mainly focused on looking at pollutants and how pollutants are breaking down in the environment.

The pollutants make it to Antarctica and the Arctic, very far from where they’re released. I was looking at their fate in the environment.

Nikki Gamble

Most of us won’t have the opportunity to travel to places that you have been to, and neither should we, because it’s important that they are preserved. But what about some of the other amazing places that you’ve been to?

Maya Wei-Haas

I now work as a freelance science journalist and travel guide. I work with National Geographic Expeditions and Smithsonian Journeys on the travel company portion of those organizations, and I travel with the guests to various locations like Patagonia and Iceland. I recently made a trip to New Zealand, and I’ll be making a trip to Alaska this summer. I talk with our guests about the amazing environments that we’re in throughout the trip. I’ll explain how things formed and how the wildlife ended up the way it did because all of these things have their deep roots in geologic history and the movement and collision of continents.

Geological activity intensely shapes the environment, not just the rocks but also the biology: the plant life and animal life that you see around you. Those stories are like the journalism I do, but I’m just telling them in person while we travel.

Nikki Gamble

This brings me to another question. I have noticed in recent years that scientists and academics are much better at communicating with a wider audience and engaging with the public.

How does the audience affect how you tell a story?

Maya Wei-Haas

 It’s an interesting question you have to tailor what you’re talking about depending on your audience.

You might be able to get into some of that depth. But the question is, what do you want your audience to take from that discussion? So, some of those details and some of that depth might not be meaningful to your audience. In this case, I don’t try to convey every single fact. I think the most important part is how you’re shaping that message and tailoring that to who you’re talking to.

When you’re talking to a general audience, you won’t tell them every single method used and all of the standard deviations that were calculated in the statistical analysis. Those things are not going to be important to them, and they won’t be what they remember.

I like to think about my stories as science mysteries that we’re trying to solve. Everything starts with a question—that’s the mystery. Then you go on an adventure to try to figure out what the answer to that mystery is. A lot of funny things happen along the way. There are a lot of missteps. There are a lot of unexpected results.

One of the things that I really try to do when I’m talking to a general audience or writing my stories, is talk about the process of science because I think that we so often learn about scientific discoveries in a very linear way. But the reality is it’s this very twisted winding thing. Oftentimes, there are happenstance discoveries. Oftentimes they’re finding things that they didn’t mean to find in the first place. Or things go entirely wrong. And, they have to entirely scramble to come up with a different way to study the phenomenon or alter the questions that they started with.

Nikki Gamble

Let’s talk about what a Rock Can Reveal. First, tell us a little bit about how the book is organized.

Maya Wei-Haas

The vision was thinking about a kid going out into nature. And asking questions and being encouraged to look at the colour, the texture, the layers in the rock and those sorts of things.

So the book starts with just some of the basic] questions   – what is a rock? What are minerals? Which was amusingly hard to define in a way that was simple enough. When you start talking about definitions of a rock as an inorganic object, you have to stop and figure out how to say that a little bit better.

After the basics, it walks through some of the questions that might come to mind as you look at these rocks. What are some of the first things that you might notice?

And then moving on the stories behind creation of the texture or the colour? The it moves on to different environments, the mountainous environment or, rocks from space and that sort of thing.

Nikki Gamble

Before we move on, I have to ask, what is a mineral? What distinguishes it from a rock?

Maya Wei-Haas

Oh, minerals. A rock is made of minerals. Minerals are generally gems or crystals; they’re a single thing. So, a single type of structure that creates a crystal, like quartz, rubies or emeralds, each of which is an individual mineral. And when you combine one or more of those together, that’s when you get a rock. You can have a really big mineral, but when we’re thinking about rocks, we’re often talking about multiple minerals mixed together.

So granite is made of different smaller minerals like quartz and feldspar. Each one of those has its own crystal structure and properties,

Nikki Gamble

Will granite always have the same minerals?

Maya Wei-Haas

That’s a good question. There is a range of different granites. Kitchen countertops come to mind when we think about home uses of granite. However, a lot of what we call granite in the kitchen countertops isn’t technically granite. Granite does have the same mix of minerals, but different types of granite can have different amounts of each of those minerals. They might be whiter if they have a lot of a particular type of feldspar and quartz. Or darker granites if they have, more smoky quartz. Or pink granite with potassium feldspar plagioclase. So there are different looks to the rocks that are all within that bigger category, but they all have the same types of minerals. It’s just the composition that changes.

Nikki Gamble

I can’t wait to pick up a rock and start looking at the different colours.

What we’re going to do next is talk about the stories of some of these rocks by focusing on some of the spreads.

I’d like to talk about volcanic rock first.

A great thing about children’s books today is that they do not talk down to children. An adult can pick this book up and learn something new, too. Before I started reading, I knew about pumice stone, and that was it. But after reading this, I learned that volcanic activity creates so many kinds of rocks. So, tell us about some of these.

Maya Wei-Haas

Yeah, volcanic rocks are just amazing. Many of the different types of volcanic rocks record motion, so I wanted to capture that in the variety of rocks we talk about on this page.

The first one is the lava bomb. These are projectiles that get flung through the air from the volcano. As they spin through the air, the molten rock is shaped into what is essentially a football. As it comes down, it whacks the ground and generally cracks off the end.

So, most lava bombs have one end that’s a little bit blunter than the other. The lava bomb, the rock that you then have, records this entire venture of the rock from flying from the mouth of the volcano through the air and landing on the ground. I have always thought that lava bombs are interesting to find because of that.

There are Hawaiian terms for two of these types of lava. The first is A A, which hurts to touch. It’s very sharp. I almost said prickly, but it’s not really prickly. It has a lot of texture to it.

And then there’s the Pahoehoe lava, which is ropey. It records the flow of the lava as it twists and moves over the landscape.

On that page, we also have Pele’s tears, which are little drops of volcanic glass. They are bits of lava that have been flung out of the volcano, similar to a lava bomb but much, much smaller. They cool down so quickly that the crystals don’t have time to form. They form this shiny, volcanic glass similar to obsidian, another type of volcanic glass that is much larger.

We also get Pele’s hair, which is the stretching of the lava as it flows through the air because it’s viscous. It’s like honey as it comes out, and as it stretches, you get those very thin hairs that freeze, which are glass. I treasure a little bit of Pele’s hair from a trip to Hawaii ages ago.

It’s spectacular to imagine the process behind each of these formations.  I’ve always thought the different types of lava are very beautiful. And yeah, they record all of the different processes.

Nikki Gamble

You’ve been to Iceland recently, and of course, Iceland has been in the news a lot because of the volcanic eruption very close to Reykjavik.

Maya Wei-Haas

Oh, Iceland, it’s scary. Scientists initially were very excited to see these eruptions because they were far from populations.

Some people refer to them as tourist eruptions because they were far from the population. You could come up fairly close safely in various ways to see them. It is an amazing display of Earth’s power.

Scientifically, it’s fascinating because they’re learning a lot about the lavas, which seem to come up from deep in the Earth, relatively unchanged. Usually, as lava erupts, it burbles up and then sits. Some crystals settle out, then the concentrate or the compounds change over time. But the lava from this volcano is different.

More recently, though, the activity has moved closer to the cities on the southern coast of the Reykjanes Peninsula. And so there’s a lot of concern for populations. There’s been a lot of back-and-forth with people having to leave their homes whenever the volcano starts erupting, and there’s a possibility of risk to life.

It’s surprising, but it isn’t surprising in that Iceland was built by volcanoes. We know that the island is there because of volcanic activity. It’s one of the few parts of the Mid Ocean ridge that sits above the sea. The Mid Ocean ridge is where the two tectonic plates are pulling apart, allowing the magma to well up and erupt.

Another thing that’s going on in another part of the country is that a hot spot sits right underneath Iceland, causing volcanoes to erupt in the south.

On the Reykjanes Peninsula, though, there hasn’t been activity for 800 years. That tends to have long periods of quiet, and then it erupts for long. We don’t entirely know why that is. We’d been in a very long period of quiet for that part of Iceland. But it seems like we’ve now transitioned into this period of frequent eruptions.

Nikki Gamble

There are so many other gems in this book. What would you like to talk about next?

Maya Wei-Haas

One of the spreads I love is the Grand Canyon spread, where the rock layers are like the pages of a book. I like to talk about how you can read them like books. So, the oldest layers are at the bottom-most unless something crazy happens and the whole thing gets flipped. But usually, the oldest layers are at the bottom, and then time passes with different layers placed on top. You can tell the story of Earth as if you are reading a book, looking at the fossils in the different layers or looking at the different types of rock in each of these layers. I think it’s just a beautiful and visual way to understand how rocks can hold stories.

When we’re talking about different rocks of the Grand Canyon, you have periods where rocks were deposited on the bottom of an ocean floor. And then, you have uplift. And so, it’s changing the types of rock sediments that are being laid down. You have light tan colours that go to these darker red colours. Then, the land sinks again, and we get different types of ocean sediments.

Nikki Gamble

We should thank the illustrator, Sonia Pulido, for making it look so beautiful.

Maya Wei-Haas

 She did a fantastic job with all of these spreads.

Nikki Gamble

How do you know the dates of these rocks?

Maya Wei-Haas

It’s a good question.

There’s no simple answer because it depends on where in the world you’re looking and what rocks you’re looking at. There are many ways that scientists can date rocks. One of them is using the] shells of a tiny creature called aiforia. They evolved to have very unique shells. Sometimes, you can tell the age of the rock from the type of aiforia that are present.

If you have bits of plant matter or something in the rock, sometimes that can be dated.

Another way is to use isotopic compositions. That’s a bit beyond my expertise, but basically, you’re looking at the breakdown of particular elements over time and using that to tell how long a rock has been there. You have to use different elements depending on how long ago. For more recent geological rocks, you can use carbon dating. Other types of isotopes can be used to date much older things.

Nikki Gamble


I’m going to invite you to make another choice for us to look at.

Maya Wei-Haas

I was thinking of the sand page because sand is often overlooked. Generally, when we think of sand, we think of yellow beach sand, but you can tell quite a few stories from just the sand.

You can get various colours of sand all over the world. I’ve tried reducing my rock collecting as I travel because we have too many boxes of rocks all over the house. However, one of the things that I still collect is sand samples. Wherever I go, I will grab just a little bit of sand and put it in a

I have several dozen vials of sand on the floor here, ranging from stark white to black.

There are pinks, greens, and everything in between. It’s like a little snapshot of the geology around you because the sand comes from the breakdown of the surrounding landscape material. So, you can get these beautiful black or green sands in volcanic environments. On islands, you often get carbonate sands from broken shell material or coral skeleton material from the creatures that live offshore. If you put any of that under a microscope, you can see some pretty amazing things. You can see the little spines of echinoderms or the tiniest aforia shells, which are beautiful.  They’re bubbly-looking or very swirly.

Sand is one of those things that we walk across and don’t think about. We use it in our gardens everywhere, but its composition is quite interesting and can tell you a lot about the environment from which it came.

Nikki Gamble

Next time I walk on the beach, I will look more closely. That’s for sure. This book is all about looking closely, isn’t it?

 Maya Wei-Haas

It is. Many things in this book are about just stopping to appreciate what is there and taking another look. A guest said something to me recently that almost made me cry. We were in Iceland in Reykjavik before setting out on the trip, and we returned there at the end. This guest said, ‘Maya, I saw this mountain off in the distance when we first visited Reykjavik. And at the time, I thought, oh, that’s a pretty mountain. But now, after I’ve spent this whole time with you and you’ve told us all these other stories, I look at that mountain differently. It’s not just a mountain anymore. ‘

With everything I write, whether books for kids, travel guides, or articles, I try to get people to slow down and think deeper about the landscape surrounding them and the long history that’s led up to the ground we’re standing on.

 Nikki Gamble

I just want to go to one more page in the book, which intrigued me. It was something that I’d never heard of before. We’re looking at a page which shows some strange mounds.

Maya Wei-Haas

Oh, the stromatolites. I have too many random fun facts, but one of my favourites is that some of our earliest lives were just mats of slime. They were microbes that bathed in the shallow waters, and they would photosynthesize, so they liked to have light.  Occasionally, they would get covered by sand, and when they did get covered by sand, these little microbes would then grow up through the sand so that they could have their light again, and then they would get covered by sand again and grow up a little bit more.

They could also create their own minerals, like layers of calcium carbonate. This activity would form lumpy mound-looking things. And that is the earliest life that we know of. When they’re in fossil form, you can cut them in half and see all of those tiny little crinkly layers.

You can visit some of their modern relatives today. The illustration in the book is based on Hamelin Pool off the west coast of Australia. Where there are these, they’re cyanobacteria mats that form into these remarkable mounds. And when you’re looking at this, you’re looking at some of our earliest ancestors. They’re really very cool.

Nikki Gamble

Amazing. That’s on my wishlist to go and visit.

 I want to get some ideas for practical activities that bring geology to life for young learners.

Maya Wei-Haas

What always caught my attention in classes growing up was when we could get out in nature. I know that isn’t always possible in a classroom environment, but I think it’s so valuable for kids to go out into their environment and ask questions. To start with a rock and ask, ‘What do you notice about this?’ You don’t have to live in a volcanic landscape to have an exciting geological history. There are these histories no matter where you are in the world.

I went to a Montessori school, which is based on hands-on activities. Rocks, geology, and earth science lend themselves very much to hands-on activities. Back in my hometown, I’m doing a series of events with kids where I’m bringing a variety of different minerals, and we’re going to test all their properties.

The pumice that we talked about floats on water. A different mineral called amber sinks when put in water, but it floats if you put it in salt water. And I think all these interesting properties of these things are really fun to test.

Calcium carbonate, if you drop a little bit of lemon juice on it, something acidic, it’ll fizz, whereas other rocks won’t do that. We have other rocks and minerals like fluorite that will glow. You can learn about the properties of these different minerals or types of rocks by playing around with them and exploring them.

Kids are like little scientists. They’re constantly trying to test their environment and the properties of everything, whether or not they know it.

Nikki Gamble

And you mentioned microscopes earlier. What sorts of things can you look at through microscopes?

You can look at things like sand because you can find many interesting things, particularly in carbonate sands, which tend to have more animal inputs.

Geologists also make what they call thin sections of rock. Rock is cut and polished until it’s paper thin and then mounted on a glass slide. Those can be viewed with a microscope that has light passing through it.

But with rocks, in general, you might not even need a microscope. You can look at large hand samples of rock just with a hand lens. So having hand lenses to be able to look at some of the crystals and look at how they grow together. Or look at the different colours and that sort of thing. You can do that just with a hand lens,

Nikki Gamble

Final question. Should children be encouraged to build rock samples, or should they leave rocks where they are?

Maya Wei-Haas

That’s a tough one. It depends on where you are. Of course, many national parks don’t want you to take rock samples because they want you to leave them where everyone can enjoy them.

But in other places, when you’re not in protected environments, I think it’s okay for kids to collect rocks. Of course, you don’t want them bringing home buckets and buckets of rocks, but often, my souvenir from a place is a pretty rock that I’ve found somewhere.

I think it’s just important to talk to students and kids about where it’s okay to collect samples and what samples are okay to take. And I always think it’s important to discuss respecting the landscape that you’re in. The rocks that I pick up are ones that are already on the ground. It makes me sad when I’m hiking around and I see an area where someone looks like they’ve taken a hammer to a beautiful outcrop.

Scientists will collect small samples from outcrops when necessary and use a rock hammer, but I think that’s a very different process than someone walking around finding a rock that they like and just whacking it to pieces.

So there’s a certain respect for the landscape that I think it’s important to have.

Nikki Gamble

Brilliant. Maya, thank you so much for dropping into the reading corner today and telling us all about what a rock can reveal. Your chat has certainly been very revealing. And I’m going to go away more observant with my hand lens and not dismiss the ground that I’m walking on. Thank you.

Maya Wei-Haas

Thanks so much for having me.