original passage: The Japanese coastal area of the sea consists of Okujiri Ridge, Sado Ridge, Hakusan Banks, Wakasa Ridge and Oki Ridge. Yamato Ridge is of continental origin and is composed of granite, rhyolite, andesite and basalt. It has an uneven bottom covered with boulders of volcanic rock. Most other areas of the sea are of oceanic origin. Seabed down to is of continental nature and is covered with a mixture of mud, sand, gravel and fragments of rock. The depths between are covered in hemipelagic sediments (i.e., of semi-oceanic origin); these sediments are composed of blue mud rich in organic matter. Pelagic sediments of red mud dominate the deeper regions.
original sentence: It has an uneven bottom covered with boulders of volcanic rock.
sentence2: If World War II required naval battles to be taken right up to the doorstep of Japan's islands, would an invasion force operating over Yamato Ridge at least be safe from submarines, given the dangerous terrain on the sea bottom?
sentence1: The Japanese coastal area of the sea consists of Okujiri Ridge, Sado Ridge, Hakusan Banks, Wakasa Ridge and Oki Ridge. Yamato Ridge is of continental origin and is composed of granite, rhyolite, andesite and basalt. The ridge has many volcanic boulders which give it an rocky, bumpy floor. Most other areas of the sea are of oceanic origin. Seabed down to is of continental nature and is covered with a mixture of mud, sand, gravel and fragments of rock. The depths between are covered in hemipelagic sediments (i.e., of semi-oceanic origin); these sediments are composed of blue mud rich in organic matter. Pelagic sediments of red mud dominate the deeper regions.