ESS 101 Lecture Notes - Lecture 15: Convergent Boundary, Plate Tectonics, Oceanic Crust

• School: UW
• Department: Earth and Space Sciences
• Course: ESS 101
• Professor: Swanson Terry

Document Summary

(1) divergent plate margin (2) convergent plate margin (3) oceanic intra-plate region (4) continental intra-plate region. Divergent plate margins: oceanic crust underlies most of the earth"s oceans; therefore approximately 70% of the earth"s surface is oceanic crust. Basalt constitutes the bulk of this crust and is produced at places where two plates are moving apart. This plate margin is known as a divergent margin; the volcanic landform produced is called an oceanic ridge. Convergent plate margins: ultimately, nearly all oceanic lithosphere is returned to the asthenosphere along convergent plate margins as evident from the observation that no oceanic lithosphere in the ocean basins is older than ~200 million years. In comparison, some continental lithosphere has been found that is as old as 3. 8-4. 0 billion years: along convergent plate margins, one plate subducts under the other plate. Magmas are generated along convergent plate margins when the subducted lithosphere is heated (due to increasing temperature with depth in the earth) and dehydrated.