Some species have colonized abyssal depths near hydrothermal vents. They are found in habitats ranging from shallow intertidal areas to abyssal depths. It lives in the mesopelagic to abyssal Pacific ocean, near the ocean floor. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. They are found from the intertidal zone down to abyssal depths, below the surface. Sediments of certain abyssal plains contain abundant mineral resources, notably polymetallic nodules. Intrusive rocks formed at greater depths are called plutonic or "abyssal". They are not generally found at abyssopelagic or hadopelagic depths or on the abyssal plain. This Bermuda Pedestal sits atop the Bermuda Rise, a mid-basin swell surrounded by abyssal plains. Most of these trench communities probably originated from the abyssal plains. The population of microbes is orders of magnitude greater than in the abyssal plains. Typically they consist of a continental shelf, continental slope, continental rise, and abyssal plain. The area below the abyssal zone is the sparsely inhabited hadal zone. The inaccessibility of abyssal habitats has hindered the study of this topic. Probably the most important ecological characteristic of abyssal ecosystems is energy limitation.