April 10, 2017
As anyone who has spent a lot of time working outside knows, field work is long and hard. I’ve been on my fair share of research trips as an observational geologist working in the tropics and learned first-hand that field work is basically made from these ingredients: stressful planning, packing hassles, long flights, inevitable food poisoning, sunburn, monotonous days, and lots and lots of fun!
Just last week, I was in the field studying how the coastline just south of the Amazon River mouth is evolving. Where did the sediment come from? Why does it stay here? Where will it go next? And how is the shape of the coastline and health of mangrove forests changing as a result? To answer these questions, we decided to survey the land to figure out the modern morphology. After days and days of work, surveying sand banks was starting to become just walking around in the blistering sun for hours holding an antenna on a pole and pushing buttons to take GPS points over and over and over again.
But just when my motivation was wavering, and a severe sunburn on top of lingering food poisoning wasn’t improving my mood, some young boys in the local community showed me just how much fun I could be having if I would just turn field work into field play. These boys, probably between 5-10 years old, would run along the exposed sandy shoals chasing our boat as we motored down the tidal channel. They’d skitter up on the muddy banks and belly slide down, back-flip off the scarps into the cool channel water, and then laugh and scream as they ran back up the bank to do it again.
From then on, we took inspiration from these young boys who were using mudbanks as slides, erosional scarps as diving platforms, and pieces of wood as snowboards. And while we were letting our inner child lead the way, we found that the sand and mud we were running and jumping on was really cool!
So what did we learn from turning field work into field play?
1. A single large stress event can cause a cool landslide.
So what’s happening here? Hurricanes bring waves and storm surges that smash into coastlines, and their energy can reach all the way down to the deep seabed. For example, Hurricane Ivan swept through Florida and Alabama in 2004 creating waves that were 40 meters high1. That’s about the height of a 12-story building! Just like a storm increases the pressure and energy reaching the seabed, jumping once on top of the sandy slope, representing the top of a submarine delta or a continental shelf, destabilizes a small part of the slope generating a minor slump. Then, this small shift in stability initiates a domino effect that cascades downwards creating more and more slumping, and eventually, a pretty substantial “landslide” several seconds after the initial jump. Big cascading submarine slumps can even create tsunamis. Scientists think that an ancient hurricane may have triggered an underwater slump that produced a tsunami at least 15 meters high over 10,000 years ago near the Mississippi River delta2.
2. Mud is slippery.
Yes, yes, I know we all already know this, but the science behind it is still cool! So, what’s going on in this video? Why can we slide down muddy banks with joyful abandon but the thought of diving belly first onto sandy slopes brings visions of immediate halts and red, scraped skin? It all has to do with the particle-water structure in mud and sand. Mud particles are really small, about the width of a human hair, and their shape is flat. When you add water to mud particles, they become partially suspended in the water and can slip past one another without much friction, creating the perfect scenario for tummy sliding. Sand particles on the other hand are much larger and more round. When you add water to sand particles, the particles aren’t suspended as much. Instead, water just sits in the pore space and sand particles stay in contact with one another, boosting friction and creating the perfect scenario for a tummy rubbed raw.
3. Crabs take offense to big survey poles encroaching on their turf and aren’t so keen on being picked up.
And what’s going on here? Well, I’m not a biologist, but I’m guessing that this crab hasn’t been inspired by all our field play yet.
Field work can be monotonous and draining if you don’t turn it into field play. I learned my lesson on this past trip and allowed field play to swoop me right out of my food and sun poisoning funk and turn me back into a spunky field researcher. Now that I’m back in my office, I’m ready to head outdoors and do it all over again!
This blog originally appeared on Robin’s blog For the Sediment Record.