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Sunday, April 25, 2010

Earthcache: Lima Coastline

I've never been much of geology enthusiast but this earthcache in Lima has peaked my interest. There aren't many caches of any kind in Lima so when any kind of cache pops up, I'm going to go after it on one of my frequent trips to Lima. Earthcache Lima Coastline (GC20EQP) was educational and just plain good exercise too. I headed out to do some running along the coastal parks that sit high above the beach. I ran several miles from my hotel and found that my GPSr was indicating that I would have to somehow work my way down the embankment to the beach. There were two choices. One was to return to a set of steps about a mile back or to go on to where I could see cars getting on to the beach along some high speed road. I ran on. When I got to the beach I found all kinds of surfers. I remembered that the Beach Boys mention surfing in Peru in one of their songs. It's true. Many were wearing wet suits. Others weren't as today was a clear, sunny day up in the 80's. The interesting think about the beach is that it wasn't very sandy at the location where the earthcache had me go. It was made up of large cobble stones. They weren't laid out as though a mason had been at work. They were simply strown everywhere. People had their beach towels laying on the stones. That had to hurt. What a beach! Where did these come from? I've always thought of Lima as a rock pile, a sort of desolate place with a gardened and irrigated wealthy residential and business districts called Miraflores and San Isidro. The truth is that it is all a big rock pile, particularly the area around the Larco Mar Mall that overlooks the Pacific Ocean. The above mentioned earthcache explained that years of river deposits left a 190 ft deep sedimentary build up called the Lima Conglomerate. "Conglomerate" is a big word that geologist use to say that rocks, in this case smooth and rounded rocks anywhere from half an inch in diameter to 10 inches, washed down to the coast and stacked up. They cemented together with the grainy mix and became a compound rock. The whole coastline at the point of the most manicured part of the city of Lima is built on a pile of rocks! After this sedimentary build up the land was gradually raised as the Nasca Plate continued to slide under the South America plate. This diverted the River that produced this sedimentary build up to the north. It is today's Rimac River. I wonder if these rocks would hold up well in an earthquake? Makes you wonder since this area is prone to earthquakes. I guess I'll sleep well tonight. I doubt I'll worry about earthquakes much since the run has worn me out. If you get a chance to check out this earthcache it is well worth the time. Yes, I climbed down to the beach and then I had to find a way to climb back up and get back to my hotel. That was a workout!
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