permafrost
n. 多年冻土;永久冻结带;永久冰冻
例句
Their roots don't grow very deep, so the permafrost doesn't interfere with their growth.
它们的根长得不深,所以永久冻土不会影响它们的生长。
Beneath this active layer is a second layer called "permafrost", which is frozen all year around, and is impermeable to water.
在这一活跃层下面,是被称为“多年冻土”的第二层,终年冻结,不透水。
There're two reasons for this: first, they live in the active layer, which, remember, contains water that doesn't penetrate the permafrost.
造成这种情况的原因有两个:首先,它们生活在活动层中,请记住,活动层中包含的水不会渗透永久冻土。