ARCHIVED CONTENT: In December 2020, the CZO program was succeeded by the Critical Zone Collaborative Network (CZ Net) ×

Northeastern Puerto Rico and the Luquillo Mountains

Field Areas     

◀Prev       Next►

The Luquillo Critical Zone Observatory (LCZO) is located in Luquillo Mountains of northeastern Puerto Rico. This Includes El Yunque National Forest, Rio Mameyes and Rio Blanco watersheds, surrounding coastal plains and nearby urbanized areas such as the San Juan metro area, Luquillo and Fajardo.

1000-5000 mm   Precip


other sedimentary, other igneous, meta-igneous, other metamorphic

Soil Order

Inceptisol, Oxisol



Areas within Northeastern Puerto Rico and the Luquillo Mountains

Jump down

Setting & Research
Overview Maps
Partner Organizations

Jump Up

  • Geology

    • other sedimentary
    • other igneous
    • meta-igneous
    • other metamorphic

    Observatory Geology
    Three principal rock types underlay the LM: volcaniclastic (VC), quartzdiorite
    (QD), and contact metamorphic hornfels (HF). Smaller out crops of basalt, mafic dikes,
    and alluvium also occur. Both types of bedrock were derived from a genetically related
    andesitic magma that was active in the lower Tertiary (Brocard this volume). The VC
    bedrock consists of thick layers of volcanic debris interbeded with shallow marine clays.
    The Luquillo Quartz Diorites are part of a system of felsic batholiths that outcrop across
    PR. Their emplacement was not accompanied by significant host rock folding but the
    associated contact metamorphism did produce the erosion resistant hornfels (HF) that
    currently forms the divide between the 2 watersheds and the highest peaks in the LM
    In general, areas underlain by the GD have faster weathering rates, sandy
    eutropeptic soils, and relatively deep subsurface flow paths (McDowell et al 1992, Brown
    et al 1995, White et al 1998, Peters et al 2006). These areas also have a higher frequency
    of landslides, well defined floodplains, and lower gradient, sandy bedded streams
    (Ahmad, et al. 1993, Larsen et al 1998, Pike 2006). In contrast, areas underlain by VC
    rocks weather to deep, clayey tropohumultic soils that have shallow subsurface flow
    paths (Silver et al 1994, Schellekens 2004), steeper hillslopes, fewer and smaller
    landslides, and relatively steep, boulder lined stream. Annual suspended sediment
    discharge can be 5 to 16 times higher under the GD that comparable VC watersheds

  • Topography

    0 - 1075 m elevation

    The Luquillo Critical Zone Observatory is located in the windward, Northeastern portion of Puerto Rico. Over a distance of 10 to 20 km, this mountain range rises from sea level to an elevation of 1075 meters. The Luquillo Mountains are the headwaters to 9 rivers that flow through steep, bedrock and boulder-lined channels until they reach their coastal plain alluvial reaches.

  • Climate

    26 °C Mean Warmest Month
    22.8 °C Mean Coldest Month
    1000-5000 mm Mean Annual Precipitation

    The Luquillo Critical Zone Observatory is located in the windward, Northeastern
    portion of Puerto Rico and in one of the wettest regions of the Caribbean. Over a
    distance of 10 to 20 km, this mountain range rises from sea level to an elevation of 1075
    meters. The Observatory has a subtropical, humid, maritime climate that is influenced by
    both orographic and global-scale synoptic weather systems. Rainfall is relatively evenly
    distributed throughout the year and increases from 1000 mm/yr in the lowlands to nearly
    5000 mm/yr at the highest elevations. Rainfall events at mid-elevations are generally
    small (median daily rainfall 3 mm/day) but numerous (267 rain days per year) and of
    relatively low intensity (< 5mm/hr). Nevertheless, individual storms with greater than
    125 mm/day occur annually, and daily rainfalls greater than 600 mm have been recorded.
    The most common disturbance-generating weather systems that affect the Luquillo
    Mountains are (1) cyclonic systems, (2) noncyclonic intertropical systems, (3)
    extratropical frontal systems, and (4) large- scale, coupled ocean-atmospheric events
    (e.g., North Atlantic Oscillation, El Niño-Southern Oscillation). Unlike some tropical
    forests, the Luquillo Mountains do not commonly have disturbances associated with the
    passage of the Inter-Tropical Convergence Zone (ITCZ) or monsoonal rains.

  • Ecosystems

    • rainforest

    See the Ecology and Forest Dynamics page for more information.