About 12,000 nautical miles of echograms (graphically recorded sea floor profiles) were obtained along straight runs between San Diego and the Marshall Islands on the Scripps Institution of Oceanography — U.S. Navy Mid-Pacific Expedition in 1950. This was the first extensive recorded profile ever obtained of the Pacific Basin so that much new topographic information was revealed.Comparison of the Pacific sea floor profile with others across the United States and the Atlantic reveals the large scale roughness of the Pacific floor, the great size of the seamounts, and the presence of broad low swells.The Hawaiian Islands are developed on one of these broad swells. Along the northeast side of the Islands there is a deep at the base of Oahu and Hawaii and an arch lying outside. It is believed the deep and the arch are related to crustal yielding in response to the load of the Hawaiian Ridge.A mountainous region with many guyots was discovered between Hawaii and the Marshall Islands which is termed the “Mid-Pacific Mountains.” A Cretaceous reef coral-rudistid fauna was dredged from the mile-deep top of two of the guyots, indicating great drowning.Exclusive of the Mid-Pacific Mountains, thirty seamounts were crossed, many of which are new discoveries. Fourteen of these are higher than 5,000 feet and six are higher than 10,000 feet. A large guyot with a summit depth of 800 fathoms was discovered north of Midway. Several seamounts appear to have a depressed zone around their bases. Nearly all seamounts probably are of volcanic origin.Three ridged scraps were crossed, viz., one 150 miles north of Bikini, another 200 miles southeast of Hawaii, and a third, the Mendocino Escarpment, west of California along latitude 40°. These ridged scarps mark abrupt regional changes in sea floor level and probably are formed by faulting.Three U-shaped depression (grabens ?) were discovered. Two of them, although separated by 1,000 miles, may be developed in the same fracture zone.Much of the sea floor is rough in topographic detail. This is especially true of the region between the U.S. and Hawaii. Sediment appears to be accumulating largely in the topographic lows forming flat basins over about 37% of the track. It seems necessary to assume that there are currents along the deep sea floor competent to erode sediment after it has once been deposited and move it into the lows.