Guam - Geography

Geography

Guam lies between 13.2°N and 13.7°N and between 144.6°E and 145.0°E, and has an area of 212 square miles (549 km2), making it the 32nd largest island of the United States. It is the southernmost and largest island in the Mariana island chain and is also the largest island in Micronesia. This island chain was created by the colliding Pacific and Philippine Sea tectonic plates. Guam is the closest land mass to the Mariana Trench, a deep subduction zone, that lies beside the island chain to the east. Challenger Deep, the deepest surveyed point in the Oceans, is southwest of Guam at 35,797 feet (10,911 m) deep. The highest point in Guam is Mount Lamlam at an elevation of 1,332 feet (406 metres).

The island of Guam is 30 miles (48 km) long and 4 to 12 miles (6 to 19 km) wide. The island experiences occasional earthquakes due to its location on the western edge of the Pacific Plate and near the Philippine Sea Plate. In recent years, earthquakes with epicenters near Guam have had magnitudes ranging from 5.0 to 8.7. Unlike the Anatahan volcano in the Northern Mariana Islands, Guam is not volcanically active. However, due to its proximity to Anatahan, vog (i.e., volcanic smog) does occasionally affect Guam.

A coral table reef with deepwater channels surrounds most of Guam. Sandy beaches, rock cliff lines and mangroves characterize the coastline area. Sheer limestone coastal cliffs dominate the north, while the southern end of the island is mountainous, with lower hills in between.