CSS Geography Geomorphology Syllabus

How does climate control landform development?

Climate determines which weathering and erosional processes dominate (e.g., glacial in cold regions, aeolian in deserts, fluvial in humid regions), producing characteristic landforms.

Who proposed the Continental Drift Theory and in what year?

Alfred Wegener, a German meteorologist, in 1912 (elaborated 1915).

What were Pangaea and Panthalassa in Continental Drift Theory?

Pangaea was the single supercontinent that existed about 250 million years ago; Panthalassa was the vast ocean surrounding it.

Into which two landmasses did Pangaea first split, separated by which sea?

Into Laurasia (Angaraland) in the north and Gondwanaland in the south, separated by the Tethys Sea.

What forces did Wegener propose drove continental drift, and why were they rejected?

Pole-fleeing force (centrifugal, due to Earth's rotation) and tidal force (gravity of sun and moon); they were rejected as far too weak to move continents.

List three major evidences Wegener gave for continental drift.

The jig-saw fit of continents (e.g., S. America and Africa), matching geological structures and rock types across oceans, and identical fossils (e.g., Mesosaurus, Glossopteris) on separated continents.

What is the apparent 'jig-saw fit' evidence for continental drift?

The matching outlines of the coastlines of South America and Africa, which appear to fit together like puzzle pieces.

Who proposed the theory of Sea-Floor Spreading and when?

Harry Hess in 1960-1962 (often called 'Hess's hypothesis').

What is the process of sea-floor spreading?

Magma rises at mid-oceanic ridges, creating new oceanic crust that pushes older crust outward on both sides; the crust is destroyed (subducted) at oceanic trenches, conserving Earth's surface area.

What key palaeomagnetic evidence supports sea-floor spreading?

Symmetrical 'magnetic stripes' (normal and reversed polarity bands) running parallel on both sides of mid-oceanic ridges, recording past reversals of Earth's magnetic field.

How does the age of oceanic crust vary in sea-floor spreading?

Crust is youngest at the mid-oceanic ridge and progressively older away from it; no oceanic crust is older than about 200 million years.

What is the Plate Tectonics Theory?

The theory (1960s) that the lithosphere is divided into rigid plates that move over the plastic asthenosphere, driven by mantle convection, and interact at their margins to produce earthquakes, volcanoes, and mountains.

What is believed to be the main driving force of plate movement?

Convection currents in the mantle (and forces such as ridge push and slab pull).

Name the three types of plate boundaries.

Divergent (constructive) boundaries, convergent (destructive) boundaries, and transform (conservative) boundaries.

What happens at a divergent (constructive) plate boundary?

Two plates move apart; magma wells up to form new crust, creating mid-oceanic ridges or continental rift valleys (e.g., Mid-Atlantic Ridge, East African Rift).

What happens at a convergent (destructive) plate boundary?

Two plates move toward each other; the denser plate subducts, destroying crust and producing trenches, volcanoes, and fold mountains (e.g., Andes, Himalayas).

What happens at a transform (conservative) plate boundary?

Two plates slide horizontally past each other; crust is neither created nor destroyed, but stresses cause earthquakes (e.g., San Andreas Fault).

Name the seven major lithospheric plates.

Pacific, North American, South American, Eurasian, African, Indo-Australian, and Antarctic plates.

What collision formed the Himalayas, and what type of boundary is it?

The collision of the Indian Plate with the Eurasian Plate (continental-continental convergent boundary).

What is isostasy?

The state of gravitational balance (equilibrium) of the Earth's crust 'floating' on the denser, plastic mantle below, like blocks floating in a liquid.

What is the basic principle behind isostasy?

Lighter crustal blocks (continents/mountains) float higher and have deeper 'roots' in the denser substratum, achieving buoyant equilibrium, analogous to icebergs floating in water.

What is the difference between Airy's and Pratt's theories of isostasy?

Airy assumed uniform crustal density with varying thickness (mountains have deep roots); Pratt assumed uniform depth of compensation with varying density (higher mountains are less dense).

What is isostatic adjustment (rebound)?

The vertical readjustment of the crust to restore equilibrium when load is added or removed, e.g., crustal uplift after the melting of ice sheets (post-glacial rebound).

What is a geosyncline?

A large, elongated, subsiding trough or basin in the Earth's crust in which thick sequences of sediments accumulate over long periods, later folded into mountains.

According to the geosynclinal theory, how do mountains form from a geosyncline?

Sediments accumulate in the subsiding geosyncline, then horizontal compressive (orogenic) forces fold and uplift these sediments into fold mountains.

What is orogeny (mountain building)?

The process of mountain formation through intense folding, faulting, and uplift of the crust caused by horizontal compressive tectonic forces along plate margins.

What are the main types of mountains by mode of formation?

Fold mountains (e.g., Himalayas, Alps), block/fault mountains (e.g., Vosges, Black Forest), volcanic mountains (e.g., Kilimanjaro), and residual/relict mountains (e.g., Aravallis).

What is the difference between an anticline and a syncline in folding?

An anticline is an up-arched (convex-up) fold forming a ridge; a syncline is a down-warped (concave-up) fold forming a trough.

What are the three main types of volcanoes based on activity?

Active volcanoes (currently erupting/likely to), dormant volcanoes (temporarily inactive but may erupt again), and extinct (dead) volcanoes.

What is the difference between intrusive and extrusive volcanic landforms?

Intrusive (plutonic) landforms form when magma solidifies below the surface (e.g., batholith, laccolith, sill, dyke); extrusive landforms form when lava solidifies on the surface (e.g., lava plateaus, volcanic cones).

What is the focus and the epicentre of an earthquake?

The focus (hypocentre) is the point inside the Earth where the earthquake originates; the epicentre is the point on the surface directly above the focus.

What are the three main types of seismic waves and their key properties?

P-waves (primary, longitudinal, fastest, travel through solids and liquids), S-waves (secondary, transverse, slower, travel only through solids), and L-waves (surface waves, slowest, most destructive).

What is the difference between the Richter scale and the Mercalli scale?

The Richter scale measures the magnitude (energy released) of an earthquake on a logarithmic scale; the Modified Mercalli scale measures the intensity (observed damage and effects) using Roman numerals I-XII.

Why can the Earth's liquid outer core be detected using seismic waves?

Because S-waves cannot pass through liquids, they are blocked by the outer core, creating an 'S-wave shadow zone,' which reveals the liquid nature of the outer core.

What is the 'Pacific Ring of Fire'?

A horseshoe-shaped belt around the Pacific Ocean margins where most of the world's active volcanoes and earthquakes occur, due to intense plate subduction.