Re: Peña Blanca - drone video
Posted by Kushad on June 5, 2021, 3:05 pm, in reply to "Re: Peña Blanca - drone video"
Pena Blanca is most likely granite. |
The colour, the texture of the way it "weathers"(geologic term) and similar in appearance to a small rock tower in the sea between La Mamz and Tamarindo that I have observed up close by boat. (Which is granite - quartz, plagioclase feldspar and biotite mica) Igneous rock - once molten.
Most of the rocks along this part of the coast are dark lava basalts that formed, likely under the sea as much as 2000 km to the west Igneous - also once molten.
The granites when still molten, were - "injected" through fractures in the now solid basalts under the surface millions of years after the basalts were formed, cooled, hardened and buried by more basalts or other? Millions of years later still, uplift and erosion of the surface stripped away the upper basalt or ?sedimentary? layers, exposing the basalt outcrops we all see out there today, with rare, scattered outcrops of granite.
Lamanz beach sand is made up mostly of ground up granite washed to the coast by rivers and transported by wave and current action along the coast. Inland in this part of Mexico, hills and mountains are predominantly granite.
Basalts (dark colour like the LaManz beach pebbles)
form primarily under the oceanic crust eg Hawaii, Big Island
If the sand were from ground up basalt, it would be black eg black sand beaches in Hawaii Big Island.
So much upheaval, movement, fracturing has happened in our area, and along much of the coast that the "geology" is very complex!
Ps I submit a very basic, somewhat conjectural interpretation of the events which are similar along the whole east rim of the Pacific Ocean as North and South America "drift" westward about 1/2" per year westward toward Asia.