Chile Triple Junction, Taitao and Tres Montes Peninsulas (South America)

Chile Triple Junction, Taitao and Tres Montes Peninsulas (South America)

Fri, 09/06/2019 - 15:14

The Chile Triple Junction is a geologic triple junction located on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula on the southern coast of Chile. Here three tectonic plates meet: the South American Plate, the Nazca Plate, and the Antarctic Plate.

The Chile Triple Junction is a geologic triple junction located on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula on the southern coast of Chile. Here three tectonic plates meet: the South American Plate, the Nazca Plate, and the Antarctic Plate.

This triple junction is an example of both a subduction and a diverging boundary. It is unusual in that it consists of a mid-oceanic ridge, the Chile Rise, being subducted under the South American Plate at the Peru–Chile Trench.

The Antarctic Plate started to subduct beneath South America approximately 14 million years ago in the Miocene epoch forming the Chile Triple Junction. At first the Antarctic Plate subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan.

As the southern part of the Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced gradually to its present position in front of Taitao Peninsula.

The Peru–Chile Trench, also known as the Atacama Trench, delineates the boundary between the subducting Nazca Plate and the overriding South American Plate.

The Chile triple junction is the only modern site on Earth where an actively spreading mid-ocean ridge crest is being swallowed by a subduction zone at a continental margin. The Chile Rise continues to spread as it is thrust beneath the continental margin of South America.

In 1960, the Chilean subduction zone was host to the largest earthquake ever recorded, a magnitude 9.8 quake that ruptured over a distance of 1,000 km (621 miles) along the Chile margin. This earthquake triggered a powerful tsunami that caused damage to coastal areas throughout the Pacific Ocean as far away as Japan.

Taitao Peninsula lies near the triple junction and various geological features, such as the Taitao ophiolite, are related to the dynamics of the triple junction.

A map of the Nazca Plate - via Wikimedia Commons
Map of the Nazca Plate: the Chile Triple Junction is located on the lower right where the Naca meets the Antarctic and South American plates.

The Taitao Peninsula is a westward projection of the mainland of Chile, with which it is connected by the narrow Isthmus of Ofqui.

It is situated in the Aysén del General Carlos Ibáñez del Campo Region and a part of this peninsula is located inside the boundaries of Laguna San Rafael National Park. The Presidente Ríos Lake, with a surface area of 352 sq km (136 sq mi), lies in the middle of the peninsula.

A southward incurving projection of the outer shoreline of this peninsula is known as Tres Montes peninsula, the most southern point of which is a cape of the same name.

The vegetation types of the peninsula vary. In the western fringes of the peninsula, towards Tres Montes Peninsula, a shrubland of around 2 m high Pilgerodendron uvifera and Nothofagus nitida grows. Amidst this shrubland occasional peatlands and forest exists. In the central parts of the peninsula, including the shores of Presidente Ríos Lake, forests of Nothofagus betuloides and Drimys winteri is to be found. Cushion peatlands of Donatia fascicularis and Oreobolus obtusangulus occupy the higher mountains of the peninsula. In the east near San Rafael Lake a Nothofagus betuloides forest with an understory of Desfontainia fulgens, Blechnum magellanicum, Fuchsia magellanica and Raukaua laetevirensgrow.

Topography map of southern Chile
Topography map of southern Chile with Taitao and Tres Montes peninsulas at far lower left

The Tres Montes Peninsula (Three Hills Peninsula) is a southwestward projection of Taitao Peninsula which in turn connects to the mainland of Chile by the narrow Isthmus of Ofqui.

The peninsula is situated in Aysén del General Carlos Ibáñez del Campo Region close to the Chile Triple Junction of the Nazca, Antarctic and South American plates.

Map of Región Aysén del General Carlos Ibáñez del Campo - via Wikimedia Commons
Map of Región Aysén del General Carlos Ibáñez del Campo, Chile