火山堑的英文：
volcanic graben

There they cool and harden into volcanic ash.
然后在空中它们又冷却变成火山灰。

An agglomerate is a volcanic breccia.
集块岩是一种火山性角砾石。

A large crater formed by volcanic explosion or by collapse of a volcanic cone.
火山口火山爆发而形成的环形山或大山核心部分的崩塌而形成的环形山

The large crater is formed by volcanic explosion or by collapse of a volcanic cone.
巨大的火山口是由火山爆发抑或是火山的崩塌形成的。

There's a mountain formed by volcanic material.
有一座由火山岩材料形成的山。

A graben creates a favourable setting for uranium deposition
地堑成为铀矿沉积的有利部位。