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Information Curtesy of Guam Visitors Bureru

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, which is 1,332 feet (406 m), and surprisingly, is also considered the tallest mountain in the world from below sea level, since it extends in to the Mariana Trench.

The island of Guam is 30 miles (48 km) long and 4 mi (6 km) to 12 mi (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.^[7] However, due to its proximity to Anatahan, vog does occasionally affect Guam.^[8]

The northern part of the island is a forested coralline limestone plateau while the south contains volcanic peaks covered in forest and grassland. A coral reef surrounds most of the island, except in areas where bays exist that provide access to small rivers and streams that run down from the hills into the Pacific Ocean and Philippine Sea.^[9] The island's population is most dense in the northern and central regions.^[6]