Rocks and Weathering Case Studies and Facts Flashcards
Similarities and Differences of Continental and Oceanic Crust
Similarities:
- both solid
- both form the crust
Differences:
- Oceanic = basaltic rocks, Continental = many types; most contain silica and oxygen, granite is most common
- Oceanic thinner = 6-10km, Continental thicker = 35-70km
- Oceanic denser = 3, Continental less dense = 2.6
Example of a Rift Valley?
East African Rift Valley
- ethiopia to Mozambique , African Plate is splitting into two plates.
Example of an Ocean Ridge?
Mid Atlantic Ridge
- Eurasian and North American plates are diverging at a rate of 2.5cm per year
Example of a conservative plate boundary?
San Andreas Fault
- North American and Pacific plates. Both plates moving in the same direction, but Pacific plate is oven 5cm a year faster.
- Caused 1989 earthquake in San Andreas = 6.9 magnitude.
Example of island arc?
Caribbean form Grenada to St Kitts.
Example of fold mountains?
Himalayas - Collision of two continental plates - Indian plate and Eurasian Plate
Andes - Oceanic and continental collision - Nazca plate subjects beneath South American Plate.
Example of ocean trench?
Marina trench = deepest part in the worlds oceans
pacific plate subjecting beneath the marina plate
Water in Hong Kong
HK receives 1900 mm of rainfall annually.
Prone to typhoons in the summer; 300mm monthly
Rock type in hong kong
HK; 85% of land is volcanic or granitic rocks = prone to landslides as weathered deeply.
Relief in Hong Kong
HK; 40% of slopes at 20-30 degrees. 20% at 30-45 degrees.
Mass movements in Hong Kong
320 landslides occur annually.
In the last 50 years, 470 people have been killed by mass movements of slopes that have been interfered with.
mass movements in HK have decreased by 50% since 1979
Deforestation in Hong Kong
Rainstroms in 1966 = slides in deforested area in HK = 64 deaths.
Mining example of mass movement
E.g Aberfan, Wales, 1966. Colliery waste dumped on top of slope = mass movement on top of school = killed 140.
Construction examples and in Hong Kong
E.g Po Shan Road landslide HK, 1972 = 67 deaths due to undercutting of slope.
HK population growth rate = 5.5% = increased construction. 7 million people live in HK
E.g Holbeck Hall Hotel, Scarborough, began descending downhill due to heavy rainfall a few months after construction.
Pinning example
E.g earth embankment on interstate 70, missouri has history of slope failures. BUT 317 pins used = no slides since 2003.
