sun_phoebus的专栏

 ocean trench 海沟plate tectonic theory 板块构造学说wobble 摇摆concentric 共心的，同心的meteorite 陨石oscillation 振动，振幅propagate （光、声音的）传播refract 折射granite 花岗岩sulfur 硫melting temperature 熔点tidal de

Internal Layers：inner core，outer core，mantle，crust。inner core : the innermost  region of the earth. It is solid and consists primarily of iron with minor amounts of light elements that likely in