HKDSE Geography/E1/Hills
< HKDSE Geography | E1
Granite Hills edit
Internal Processes | External Processes | Rock Types | Human Activities |
---|---|---|---|
Intrusive Vulcanicty - Batholith Intrusion | Denudation:
|
Granite | / |
Characteristics:
- Low
- Rounded
- Thick weathering profile
Underlying reasons: Non-resistant and well-jointed → Chemical weathering ↑ → Erosion ↑ → Mass Movement ↑ → Low and rounded, thick colluvium layer
Formation:
- Magma in the asthenosphere is under great pressure.
- A line of weakness develops in the crust and reaches the magma chamber below.
- The magma rises through the line of weakness and into the earth's crust.
- It cools and solidifies at a very slow rate in a dome-shaped magma reservoir. Crystallisation occurs.
- It becomes a plutonic rock called a granite batholith.
- As Hong Kong's climate is hot and wet, active chemical weathering and erosion remove the layer above.
- The batholith is exposed to the surface to produce granitic hills.
Examples:
- Both sides of Victoria Harbour
- Castle Peak and Tai Lam Chung
- Shatin
- Northern part and southernmost tips of Hong Kong Island, the northeastern part of Lantau Island, most of Lamma Island, Po Toi Island, and the Soko Islands
Tuff Hills edit
Internal Processes | External Processes | Rock Types | Human Activities |
---|---|---|---|
Extrusive Vulcanicty | Denudation:
(Very little occurs) |
Tuff | / |
Characteristics:
- Rugged and uneven
- High
Underlying reasons:
- High resistance, few joints → Less chemical weathering → Less erosion → Less mass movement → Higher, rugged
Examples:
- N/E/Central NT (e.g. Tai Mo Shan, Sai Kung)
- Western Lantau (e.g. Lantau Peak), southern Hong Kong Island
Sedimentary Rock Hills edit
Internal Processes | External Processes | Rock Types | Human Activities |
---|---|---|---|
/ | Differential Erosion | Mechanically-formed sedimentary rocks:
|
/ |
Characteristics:
- Uneven
- Varying Height
- Ridges
Underlying reasons:
- Non-resistant and well-jointed (e.g. shale) → Chemical weathering ↑ → Erosion ↑ → Mass Movement ↑ → Low and rounded, thick colluvium layer
- High resistance, few joints (e.g. conglomerate) → Less chemical weathering → Less erosion → Less mass movement → Higher, rugged
Examples: