The Antarctic Peninsula is 600 miles to our stern; The wonders of the seven seas On February 5th, 2025, I approached Argentina and docked it. Located along the coast of the Beagle Channel on Tierra del Fuego Island. I’ve been walking the streets and hills of Ushuaia many times, so instead of trying it over again, I signed up for a trekking to the heart of the sturdy mountains.
Part 1 – Inland Trekking in Terra del Fuego
An approach to Ushuaia with the mountains of Tierra del Fuego.
First, a few places. This is simply a map of the Isla Grande de Tierra del Fuego, outlined in yellow. The Ushuaia and Punta Arena, which are shown for reference, also show the tracks of greatness. Note that the south and north of the island’s mountainous region are modest coastal plains. Isostatic loads, glacial erosion, and (in some cases) faults are responsible for a large eastward bay towards the west (left) side of the island.
Zoom in a little more and see the active Magalan-Fagnano fault system (yellow line). This is the left strike slip fault that separates the South American plate (top) from the Scotia plate (bottom). The highest elevation shown (south of the fault) is part of the Darwin range (glaciers emanating from this range are shown at the end of this post). The white line fills another linear valley. There, trekking takes place, strangely paralleling the main transformed valley. See this paper for a recent discussion of slip rates on this obstacle.
About 20 miles north of Ushuaia (Pan American Highway, Argentina) we arrived at the valley where the trek began. This valley runs parallel to Lake Fagnano, where the Magalan Fagano fault is located, and south of the valley (the fault lies behind the serrated peak that appears in the skyline). Note that there is also a thrust fault just below the sawtooth peak. Here, Jurassic upper volcanoes and sedimentary sequences (called dark rocks and Tobifera FM) pierce the lower Cretaceous marine rocks (light colour and also slightly metamorphosis).
Close-up of Tobifera volcanic deposits (slightly metamorphic).
We encountered a large beaver dam at the end of our hike. The Beaver was brought to Tierra del Fuego in the 1940s, hoping to create demand for fur. However, the area was much warmer than the native North America, and the fur was of poor quality. The beavers remained and created ecological disasters in the local ecosystem. Several efforts have been made to eradicate them, but so far they have been successful locally.
A U-shaped valley formed by Pleistocene glaciers. The entire south side of Tierra del Fuego was overrun with ice.
Part 2 – Evening Cruise at Beagle Channel and Cordillera Darwin
Wonderfulness Departs from Ushuaia at 8pm. This view of the south heads towards Islanavarino in Chile. The Beagle Channel serves as an international boundary here.
This is a view that follows the traces of the Beagle Channel, heading back east towards Ushuaia.
However, when we saw a higher peak in Cordillera Darwin, the cloud parted ways. The glacier flows from height to the Southern Patagonia Basolis. This is a series of granite invasions (some young invasions) established in the Late Jurassic period between 157 and 145 MA. These granite bodies are a possible source of Tobifera volcanic deposits found on trekking in the previous section above.
This photo was taken at 8pm local time.
It’s somewhat unusual for the peaks of this area to be free from winds and clouds, but once again it was a great experience.
The mountain here reaches an altitude of approximately 9,000 feet from the sea level.
Ice spills from the mountains over ice age-free terrain.
Note the moraine in the center of the photo.
Many of the names of the glaciers in this stretch come after countries such as Italy, Romania, and Germany. This is an Italian glacier (glacial Italy). The name honors the nation that took part in the survey, which was photographed in the area during the transport of Venus in 1874.
The image of an Italian glacier, photographed in 2008, shows the recession. The photos are from a paper dealing with the extent of these glaciers from the small glacial age that can be accessed here.
Aremania (Germany) Gracia.
Romance (Romania) Glacier. I love Tierra del Fuego!
