GEOS 1004 Lecture Notes - Lecture 17: Water Cycle, Continental Crust, Cyanobacteria
Document Summary
Lecture 17: history of the earth"s surface; hydrologic cycle. Given off as gas during volcanism ; +co2 and n2 (create atmosphere), not h2 (escapes to space). First record of water - first sedimentary rocks; 4. 0 b. y. ago. Earth history compressed into a year: 4 billion years = st. valentine"s day. Landmasses emerge gradually ~3 billion years ago due to plate tectonics (making of continental crust). Between 4. 0-3. 0 billion years, there is no land- earth is covered by continuous ocean: atmosphere. Initially dominated by co2, h2o, methane, ammonia due to volcanism. 2. 5 b. y. ago - oxygen begins to accumulate. 1. 0 b. y. ago - oxygen levels approach today"s was reducing ( ferrous iron, fe2+, which is soluble). The early ocean oxidizing (fe is ferric, fe3+, which is insoluble). Banded iron formations= chemical sediment, iron oxide (hematite), precipitated when oceans became oxygen rich. 2. 5 billion years ago = 50 c since then varies 5 -30 c: climate.
