Topography
APRA HARBOR, GUAM
TOPOGRAPHY
Guam is about 30 nmi long and varies from 4 to 8 nmi in width. Guam is reef-fringed, which dries in spots, over a greater part of its shoreline. From a distance the island appears flat and even. The north end of the island is a plateau of rolling hills set on vertical cliffs rising to about 490 ft (149 m) above sea level. The south end of the island consists of high volcanic hills. The plateau is covered with a thick growth of jungle. The volcanic hills support mainly sword grass. The highest hills are found in the central and south parts of the island. Guam has elevations exceeding 1,000 ft (305 m) above sea level (Figure II-31).
The highest point on Guam is Mount Lamlam a 1,332 ft (406 m) peak located approximately 5.5 nmi south of the middle of Inner Apra Harbor. The second highest point on the island is 1,242 ft (379 m) Mount Jumullong Manglo, located close to and southeast of Mt. Lamlam. Mount Alutom, a 1,074 ft (327 m) rise, is located approximately 2.5 nmi east of the Inner Harbor. Several other peaks exceeding 900 ft (274 m) in elevation are oriented generally on a north-south line extending southward starting about 3 nmi south of the Inner Harbor.
The northern half of Guam is less rugged, with 828 ft (252 m) Mount Santa Rosa being the highest point. Other significant elevations include 656 ft (200 m) Mount Barrigada near Agana and 602 ft (183 m) Mount Machanao near Ritidian Point on the north end of the island. Away from the steep rises located in several coastal areas, most of the terrain of northern Guam is characterized by gently sloping, wooded inclines and valleys. Several areas of Guam 's coastline drop precipitously into the sea. The more dramatic examples are the 300 to 600 ft (91.4 to 182.9 m) high cliffs on the northeastern and eastern coasts of the island.
Except for a minor blocking effect of east or southeasterly winds, the terrain of the island does not significantly affect winds at Apra Harbor.
Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/guam/apra/text/sect5.htm
