With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: 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 even bottom made of flattened volcanic rock, rather than the usual jagged boulders. 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.
text_B: Does the passage suggest that undersea volcanoes tend to leave behind smooth, glassy plates of hardened lava in the same way that they do on land, or, at least, that sea water tends to grind down volcanic rock quite readily?
YES.