Seamount Abundances and Distribution Near the East Pacific Rise of O deg-24 deg N Based on Seabeam Data

摘要

We used 10,240 line km of Seabeam data to study the sizes, abundances and distribution of seamounts near the East Pacific rise (EPR) from the equator to 24 deg. N on lithosphere <10 Ma. We find 168 volcanoes with heights over 50 m in this study area of 18,400 sq km for a mean seamount abundance of about 9000 seamounts/million sq km or 1.5 million seamounts for the Pacific assuming constant production rates. Abundances in 49 undivided 1 deg x 1 deg areas vary widely from values of zero to over 66,000 seamounts/million sq km after linear adjustment for percent of area coverage in each 1 deg square. This indicates highly non-uniform distribution and, in fact, most seamounts are clustered near transform and fracture zones, some large overlapping spreading centers (OSCs) and swollen elevated portions of the EPR. Seamount abundance within 50 km of the EPR is about 10,000 + or - 6000/million sq km and does not seem to change significantly out to 550 km from the EPR crustal age (4-9 Ma). Size frequency distribution shows similar patterns for 0-0.5 Ma and 0.5-1.0 Ma sea floor, with 70-80% of the volcanoes being smaller than 0.1 cu km (<100 m high); on older crust, however, only about 45% are in this small size class. If representative, these data indicate that most small seamounts are produced very near the EPR and some may continue to grow as they drift away. Seamount production appears to be strongly linked to tectonic an petrologic processes at the EPR near major transform offsets and possibly at some large OSCs. (EDC)