1.
sedimentary rock
One of the three main categories of rock, formed when particles such as sand, mud, shell fragments, or dead organic matter accumulate in layers and are gradually compacted and cemented into solid stone. Sandstone, mudstone, limestone, and shale are all sedimentary rocks.
砂岩は堆積岩の一種だ。
Sandstone is a type of sedimentary rock.
堆積岩には化石が含まれていることがある。
Sedimentary rocks sometimes contain fossils.
川や海の底に積もった砂や泥は、長い時間をかけて堆積岩になる。
Sand and mud piled up on riverbeds and sea floors become sedimentary rock over long periods of time.
地層を観察することで、堆積岩が作られた当時の環境を推測することができる。
By observing the strata, we can infer what the environment was like when the sedimentary rock was formed.
Composed of 堆積 (accumulation; piling up) + 岩 (rock). A standard term from earth science, used from elementary-school textbooks through university geology. Sedimentary rocks are particularly important in Japan because many geological formations — and most fossil sites — lie in sedimentary strata.
COMMON COLLOCATIONS:
- 堆積岩の地層: layers of sedimentary rock
- 堆積岩に含まれる化石: fossils contained in sedimentary rock
- 堆積岩が形成される: sedimentary rock is formed
- 堆積岩の種類: types of sedimentary rock
MAIN TYPES OF SEDIMENTARY ROCK:
- 砂岩: sandstone — formed from sand-sized grains
- 泥岩: mudstone — formed from very fine mud particles
- 頁岩: shale — a finely layered mudstone that splits into sheets
- 石灰岩: limestone — formed from the calcium carbonate of shells and marine organisms
- 礫岩: conglomerate — formed from rounded pebbles and rock fragments
RELATED TERMS:
- 火成岩: igneous rock — formed from cooled magma or lava
- 変成岩: metamorphic rock — rock that has been transformed by heat and pressure
- 地層: stratum; geological layer — the layered formation in which sedimentary rock typically appears
- 化石: fossil — the preserved remains or traces of ancient life
- 堆積: sedimentation; accumulation
USAGE:
The three-way classification 火成岩 / 堆積岩 / 変成岩 is standard in Japanese science education and natural history museums. Students typically learn it in middle school.