Back درع (طبقات الأرض) Arabic Qalxan (geoloji termin) Azerbaijani Щит (геология) Bulgarian Escut (geologia) Catalan Štít (geologie) Czech Tariandir Welsh Schild (Geologie) German Ηπειρωτική ασπίδα Greek Escudo (geología) Spanish Kilp (geoloogia) Estonian
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| Extended crust | Oceanic crust: 0–20 Ma 20–65 Ma >65 Ma |
A shield is a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas.[1] These rocks are older than 570 million years and sometimes date back to around 2 to 3.5 billion years.[citation needed] They have been little affected by tectonic events following the end of the Precambrian, and are relatively flat regions where mountain building, faulting, and other tectonic processes are minor, compared with the activity at their margins and between tectonic plates. Shields occur on all continents.
- ^ Kearey, P. (2001). The new Penguin dictionary of geology (2nd ed.). London: Penguin. p. 243. ISBN 0-14-051494-5. OCLC 59494925.