Where do divergent boundaries happen mostly?(2)
- -mid ocean ridges
- -continental rift
What are divergent boundaries?(3)
- -normal faults
- -makes new crust
- -new oceanic lithosphere forms
Describe the process of mid-ocean ridges?
- § Oceanic crust form through sea-floor spreading, hot asthenosphere melts molten rock. Magma forms and rises then accumulates in ridge (magma chamber)
- § As plates move away from the MOR
- axis, they cool and the lithosphere mantle forms and thickens
What are the properties of mid-ocean ridges? (6)
- § Intrusive and Extrusive
- § Felsic rock SiO2 rich
- § Sedimentary rock -> limestone,
- chert, biochemical rocks
- § Decompression (less pressure)
- § Segmented, denser, thin crust
- § Metamorphic-> hydrothermal
What is a continental rift?
- § A linear belt in which continental
- lithosphere pulls apart
- ·Stretches horizontally and thins vertically
- Fault: Normal
Why does melting happens at continental rifts?
Melting happens because the crust thins
What kind of rocks form there?
Name some rocks seen there.
- metamorphic rocks and igneous rocks
- § Igneous rock: Basalt, Rhyolite and andesite (intermediate)