|La Portada Natural Monument|
|Location||Antofagasta Region, Chile|
|Governing body||Corporación Nacional Forestal|
The arch of La Portada is 43 m (140 ft) high, 23 m (75 ft) wide, and 70 m (230 ft) long. It has a base of black andesite stone, around which are arranged marine sedimentary rocks, a stratum of yellowing sandstone, and layers of the remaining fossils of shells dating back 35 to 2 million years ago. All this was formed during a long process of marine erosion.
The arch is surrounded by coastal cliffs that were also formed by marine erosion. They reach a maximum height of 52 m above sea level.
On 5 October 1990, it was declared a natural monument under Supreme Decree #51 of the Ministry of Agriculture, published in the Diario Oficial.
Since March 2003, this natural monument remains closed due to a landslide of an important part of its cliffs, which blocked access to its beach. For this reason, a remodeling of the access route and its surroundings is planned.
The natural monument constitutes an observation site for guano birds such as Peruvian booby (Sula variegata) and Inca terns (Larosterna inca), as well as Guanay cormorants (Phalacrocorax bougainvillii), kelp gulls (Larus dominicanus), grey gulls (Larus modestus), Belcher's gulls (Larus belcheri), and pelicans.
La Portada is located 18 km (11 mi) north of Antofagasta, which can be accessed by Route 1 Antofagasta-Tocopilla, from which an access road diverges at kilometer 20.