Across
- 3. relating to the earliest known rocks formed during the Precambrian Eon
- 4. movement of the edge of one tectonic plate under another
Down
- 1. the branch of geology studying the folding and faulting of the earth's crust
- 2. a grey tetravalent metallic element that resembles zirconium chemically and is found in zirconium minerals; used in filaments for its ready emission of electrons