Geological Typologies

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Asia City Geoscience Profiles Home >> Geological Typologies

For these City Profiles we have divided each city's geological setting into specific typologies, or classes, as shown in the table below.

Geological Typologies
Geological setting Summary of geological characteristics Examples in Asia Geological challenges Geological opportunities
'Soft-bedded' cities

Underlain by significant thicknesses (at least 200m?) of unconsolidated sediments

DELTA Sediments deposited by interaction of fluvial and marine processes. DHAKA, Kolkata, HO CHI MINH CITY, Yangon Subsidence; flooding; sea level rise; lack of aggregate resources; salinisation of groundwater; unstable building conditions Uniform subsurface conditions; flat land; groundwater resources
Alluvial basin/ river plain Sediments deposited by fluvial processes. Varanasi, Delhi, Lucknow, Phnom Penh, Patna, Mandalay, Can Tho, Hanoi Subsidence, flooding; lack of aggregate resources; unstable building conditions Groundwater resources; uniform subsurface conditions; flat land
Coastal plain Sediments deposited by marine processes, with minor marine input. Medan, Jakarta, Surabaya, Chenai, Da Nang, Malacca
'Hard-bedded' cities

Underlain by consolidated bedrock. The upper part of the bedrock, up to tens of metres thick, is often weathered; and there may also be a thin covering (eg up to 30m?) of unconsolidated deposits overlying bedrock. Geological properties are highly dependent on the bedrock type (sedimentary, metamorphic, volcanic, intrusive igneous). However, the subdivisions below are considered useful

Low relief Developed in tectonically quiet regions, with slow weathering erosion processes over long periods of geological time. Hyderabad, Mysore, Bangalore, Nagpur, Jaipur, Pune Highly irregular weathering front/rockhead; variable ground (subsurface?) conditions; limited groundwater No subsidence; stable ground (subsurface?) conditions (BUT WEATHERING?); aggregate resources
High relief Developed in tectonically active regions, with pronounced topography. Singapore, Hong Kong Highly irregular weathering front/rockhead; variable subsurface and ground conditions; limited groundwater; landslide risk Abundant aggregate resources; no subsidence; stable ground (subsurface?) conditions
'Complex-bedded' cities

Contain two or more elements of low and high relief settings

Mixed 'hard-bedded'/'soft-bedded' Underlain in part by bedrock (sometimes of very different types) and in part by thick unconsolidated sediments. Kuala Lumpur, Mumbai Highly irregular weathering front/rockhead; variable ground (subsurface?) conditions
Intramontane basins A special case. Not described here. Kathmandu, Tehran Seismic risk, landslide risk