The volcanic field covers an area of about and consists of about 100 observed volcanic cones with associated lava flows. The volcanic cones range from shield-like to steep to lava dome-like and long ridges and lava flows range from lava lakes forming flat-topped cones to over long lava flows despite the flat terrain; small hills in the lava flows may be vents. The average thickness of the lava flows probably amounts to either less than or about . Fissure vents also occur in the field; one of these has been the source of a lava flow. Owing to the sizes of the lava flows, the field has also been called a flood basalt in analogy to its usually much larger continent-based counterparts. The volcanoes are located among Cretaceous seamounts and sediment-covered seafloor, which forms kipukas between the lava flows. In turn, lava flows are covered with over thick sediments. A noticeable swell where clusters of volcanic cones occur may reflect the presence of sills. The total volume of the volcanic field is about , much less than a typical Hawaiian shield stage volcano, and rocks occur in the form of e.g. glass shards, pillow lavas, scoria and volcaniclastic material. A seismic velocity anomaly at depth appears to be associated with the North Arch volcanic field.