Tag Archives: geology

The Water Cycle and The Future

I’ve always loved water. My favourite sport is swimming, because of how it feels to have water holding you up. And when I was young, any time it rained I’d run outside and just walk for ages in the rain: I loved the smell and the cool of it. Admittedly, rain was a rarity in my childhood, since I grew up in New Mexico in the US, which is all mountains and desert. I can see why here in Ireland, where rain is so much more common, you see fewer people rushing to the streets each time it rains. But in my desert home, one of the things I found fascinating is that water has a story, a history just like us, it has somewhere it came from and somewhere it’s going. When we see the rain fall, it’s evaporated from the ground, from lakes, from the sea. And that same rain will be absorbed by the ground and stay in it before rising again, or freezing into ice caps, or melting and flowing again to the sea. Here in Ireland, the clouds come in off the ocean, so the water in our rain is evaporated sea water.

We can think of the water on the world like the water in our own bodies. We can run and get sweaty, and the water on our skin evaporates away. We can drink in water, filling our insides the same way that aquifers under the surface of the earth are filled with water. And then we can release that water given time, the same way that solid land loses some of its water to the seas. But because the earth is so big, it also has weather on its surface, clouds and rainfall, and as far as I know I’ve never sweated enough to make it rain.

But how quickly water moves through this cycle depends on the weather, the same way it does for our bodies. You sweat more when it’s hot and humid, like now, and less if it’s cold or dry, right? Well water is affected the same way, by how warm the surface of the earth is. In hot conditions, more water will evaporate off the earth’s surface and off of plants, which can stimulate more weather like rain and thunderstorms… unless it’s very dry! So where I grew up, desert plants have to work really hard to hang onto water, because it’s such a precious resource and the heat and dryness cause it to go away really quickly. Plants here don’t have that issue, as there is plenty of water to go around!

We are changing how the water cycles through our world, though. When people build dams, cut down forests, pasture animals, build cities, or burn fuel for energy, that changes where water can flow and how long it stays in the air. All of our activities affect the flow of water through the sky, the sea, and the earth.

In fact, greenhouse gases from our human civilization are causing the atmosphere to trap more heat from the sun, so that our planet is gradually warming up. It’s a slow process, taking decades for the world’s temperature to rise even a degree on average, but it’s been going on for awhile now. So even though we are trying to switch to solar power away from things like coal power, our planet will keep warming up. Sea levels will go up, and we’ll have warmer summers and rainier winters. Here in Ireland, it might be nice, as long as you don’t live right on the sea. But in New Mexico, it’s already difficult to grow food and stay cool during the summer, so the extra heat might make it very hard for people to live there. But the important thing about the future is understanding it so you can plan accordingly… for example, by moving to Ireland!

Understanding ‘Deep Time’

One of the most challenging things I’ve tried to explain in my science communication career is the concept of ‘deep time’, or the geological timeline of the earth. While it is crucial to understanding the history of the Earth and life as we know it, the vast span of time involved can be an incredibly difficult concept for young people to grasp – and rightly so. When an 8-week summer term can feel like an idyllic lifetime, 4 billion plus years is mind-blowingly huge. However, having a strong conceptualization of scale and the relationships between scales is essential in being a scientifically literate consumer of information (Tretter, et al., 2006), so how do you explain geological time in a way that young people can grasp?

An important engagement tool is helping people to relate to the facts you’re telling them, making them invested in learning more rather than counting on them to want to gain knowledge just for knowledge’s sake. Many educators use the hook of human existence when explaining geological time, which not only interests the audience but gives an excellent reference to the vastness of scale with which you are dealing.

You could try to calculate it out in numbers: The history of life on Earth began about 3.8 billion years ago, initially with single-celled prokaryotic cells, such as bacteria. Multicellular life evolved over a billion years later and it’s only in the last 570 million years that the kind of life forms we are familiar with began to evolve, starting with arthropods, followed by fish 530 million years ago (Ma), land plants 475Ma and forests 385Ma. Mammals didn’t evolve until 200Ma and our own species, Homo sapiens, only 200,000 years ago. So humans have been around for a mere 0.004% of the Earth’s history. (http://www.bbc.co.uk/nature/history_of_the_earth)

Many people turn to analogies, those things which are like… other useful things. For example:

The 24-hour clock: Did you know…that if we compress the Earth’s 3.7 billion years existence to a 24-hour time scale, the first human species appeared about 47-94 seconds before midnight, and our species (Homo sapiens) appeared roughly 2 seconds before midnight? (http://www.rigb.org/contentControl?action=displayContent&id=00000001056)

Clocks are actually a very common visualisation tool: http://deeptime.info/

The book of the world: If you were to write a history of the Earth’s past, allowing just one page per year, your book would be 4,600,000,000 pages long. That’s a very thick book — 145 miles to be exact. An average reader, reading about 1 page every 2 minutes would need more than 17,503 years to finish it. And that’s with no time out for anything else — no time to eat, sleep, ride a bike, or go to school. Even if you were an amazing speed reader and could read 2 pages every second, it would still take you nearly 73 years to read the entire book. (http://www.ucmp.berkeley.edu/education/explorations/tours/geotime/)

You can even get creative with a roll of toilet paper:

One of my favourite ways to explain just how long the earth’s timeline stretches is to hold out my arm and ask my audience to imagine the entirety of the earth’s history is represented along its length. It’s billions upon billions of years old, and things changed verrrrry slowly. The first life – bacteria – started forming here, around my bicep, and oxygen didn’t even start building up in the atmosphere until around here, my elbow. After that things start developing a bit more quickly, with blue-green algae appearing here, eukaryotic cells here, and down by my wrist the first multicellular organisms finally enter the story. In just the short span of my hand most of the life we know evolves and flourishes, and eventually – at the very end – human beings appear. How long have they been around, in the grand scheme of things? No more than the sliver of my fingernail at the end of my middle finger. So while we like to think that humans are the dominant species, superior to all others, in the grand scheme of things we’re newcomers on this planet – ones who could be erased with the flick of a nail file!

And just in case you were wondering how things stacked up in a galaxy far, far away: http://io9.com/5890342/a-chart-that-explains-how-long-ago-star-wars-actually-took-place