also: ちんじょうようがん
noun
pillow lava
Geological term for lava that solidifies underwater into characteristic pillow-shaped formations.
枕状溶岩は海底火山活動の証拠として重要だ。
Pillow lava is important as evidence of submarine volcanic activity.
この地域の枕状溶岩は約1億年前に形成された。
The pillow lava in this area was formed about 100 million years ago.