Tropical Geophysics: a post-trip report

I not-so-recently returned from not zapping zebras, my first experience with tropical fieldwork for geophysics.

Packing List

Aside from the usual collection of field gear and the semi-standard collection of tropical-medication, my retroactive absolute must-pack list includes:

An umbrella is remarkably handy for short, sudden downpours.

An umbrella is remarkably handy for short, sudden downpours

  • Acquiring jugs or buckets was not a problem, but tarps are harder to find and worth packing. An umbrella is shockingly useful for sudden short downpours.
  • bug net: to gain a few moment’s peace when attempting to repair equipment.
  • the usual collection of spare batteries x3: they’ll last longer, but everyone wants to keep your AAs & 9Vs.
  • plastic sealable bags & boxes: prevent mildews & everyone wants to keep them — a box of ziploc bags buys a lot of goodwill.
  • sunglasses & hat x2: not necessary every day, but going-without if one disappears is not an option
  • tasty multivitamins: endless beans and rice lacks a few nutrients
  • sugary drink powders (Crystal Lite, Gatorade, CoolAid): a tasty alternative to rehydration salts when plain water doesn’t keep up with the sweat.

Tropical Geophysics

Batteries run the lives of most geophysicists. Working in the tropics is amazing, as battery voltage readings actually increase for the first few hours of the day as weather and instruments warm up. I didn’t need to swap out batteries nearly as frequently as in temperate fieldwork, to the point I stopped bringing my spares into the field and left them at the base-truck.

grassIn Africa during the wet season, grass is “short” if you can see over it, “tall” if you can’t, and “very tall” if you’re left in bafflement over how something is so tall it’s still grass and not a tree. This makes straight lines a bit of a challenge. GPS-marking each measurement station and taking notes on cross-line points is good standard practice for in any environment, and downright useful when working in flat terrain at equatorial latitudes with enough satellite locks to obtain ±5m accuracy. (In mountainous, thickly-forested BC, ±30m is distressingly common.)

Flash floods are a common event during the wet season.

Flash floods are a common event during the wet season.

The wet season also meant that on a few occasions, I needed to abruptly shorten data collection due to sudden flooding, or thunderstorms making electrical surveys too dangerous to continue. When working with an array that did not require manually moving points to take readings, I found it useful to collect low-density data first, then infill with additional datapoints if weather permitted. With a mobile survey, adding timestamps to fieldnotes lets me track average and current productivity, so I could change station density on the fly to collect as much data as possible before end-of-day (or faster, if weather was worsening to a dangerous state).

Crew packing equipment out at the end of a field day.

Crew packing equipment out at the end of a field day.

Unlike Canada, where field time (especially in the winter) is typically limited by daylight hours, I found African field time more limited by the heat of the day. Although my crew of locals was understandably infinitely more acclimatized to the weather than I was, even they found hauling heavy equipment in the late afternoon sun too much. Similar to working with explosives for seismic surveys during high fire danger, we had to shuffle field-days to start early/end early to avoid heat stroke.

Key Post-Trip Cleaning Tip

Large spiders make poor stow-aways.

Large spiders make poor stow-aways.

Tropical hitchhikers in the form of terrifyingly huge bugs are not uncommon; my gear was in prolonged cold-isolation, then carefully inspected before returning to field rotation to avoid waking up next to palm-sized spiders once I got home.

After 40 days of washing my clothes with shampoo in the sink and trying to air-dry them in endless storms, my gear came back absolutely reeking of sickly sweet foot-cheese mildew. Running them through the wash multiple times didn’t help. Soaking them for 24 hours in a mix of water, white vinegar, and baking soda completely eliminated the stench (followed by a regular launder so I didn’t smell like a science experiment).

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