What is plate tectonics? — The scientific theory that Earth's lithosphere is divided into large plates that move slowly (a few cm/year) over the asthenosphere. Their interactions cause earthquakes, volcanoes, and mountain building.

What are the three types of plate boundaries? — Convergent: Plates move toward each other (subduction or collision). Divergent: Plates move apart (ocean ridges, rifts). Transform (conservative): Plates slide past each other horizontally (e.g., San Andreas Fault).

What happens at a convergent boundary? — Plates collide. If oceanic meets continental: oceanic plate subducts (sinks), forming a trench and volcanic arc. If continental meets continental: fold mountains form (e.g., Himalayas).

What happens at a divergent boundary? — Plates move apart, creating a gap. Magma rises to fill it, creating new oceanic crust. Forms mid-ocean ridges (e.g., Mid-Atlantic Ridge) or rift valleys (e.g., East African Rift).

What is a subduction zone? — Where a denser oceanic plate sinks beneath a less dense plate into the mantle. Creates deep ocean trenches, volcanic arcs, and earthquakes. Example: Pacific Ring of Fire.

What is the Ring of Fire? — A 40,000 km horseshoe-shaped zone around the Pacific Ocean with ~75% of Earth's volcanoes and ~90% of world's earthquakes. Caused by multiple subduction zones surrounding the Pacific Plate.

What is the Richter scale vs Moment Magnitude Scale (Mw)? — Both measure earthquake magnitude. Richter scale: Older system, each unit = 10× more ground motion. Mw (Moment Magnitude): More accurate modern scale used for large earthquakes. Both are logarithmic.

What is the difference between focus and epicentre of an earthquake? — Focus (hypocentre): The underground point where the earthquake originates. Epicentre: The point on the surface directly above the focus — where shaking is usually strongest.

What is a shield volcano vs a composite volcano (stratovolcano)? — Shield: Low, broad, gentle slopes. Basaltic lava, non-explosive. Example: Mauna Loa, Hawaii. Composite: Steep-sided, cone-shaped. Alternating lava and ash layers, violent eruptions. Example: Mount Fuji, Vesuvius.

What are the four processes of river erosion? — Hydraulic action: Force of water breaks rock. Abrasion: Rock particles scrape and wear the channel. Attrition: Rocks collide and break into smaller pieces. Solution (corrosion): Water dissolves soluble rocks.

What are the four processes of river transportation? — Traction: Large boulders rolled along the bed. Saltation: Pebbles bounced along the bed. Suspension: Fine particles carried within the water. Solution: Dissolved material carried invisibly.

What is a waterfall and how does it form? — Forms when a river flows over a band of hard rock overlying softer rock. The softer rock erodes faster, creating a step. Hydraulic action undercuts the hard rock, forming an overhang that collapses — the waterfall retreats upstream.

What is an ox-bow lake and how does it form? — A crescent-shaped lake formed when a river meander is cut off. As a meander tightens, the river breaks through the neck during a flood, taking a shorter path. The old loop is sealed by deposition, forming an ox-bow lake.

What is a river delta and what types exist? — A landform at the mouth of a river where sediment is deposited as the river slows entering the sea. Arcuate (fan-shaped): e.g., Nile Delta. Bird's foot: e.g., Mississippi Delta. Cuspate (tooth-shaped): e.g., Ebro Delta.

What is hydraulic action at the coast? — Waves trap and compress air in cracks in the cliff face. When the wave retreats, the compressed air expands explosively, breaking off rock fragments. Also called wave quarrying.

What is longshore drift? — The zigzag movement of sediment along a coastline. Waves approach at an angle (driven by prevailing winds), carrying sediment diagonally up the beach. Backwash returns sediment straight back down the beach.

What is a spit and how does it form? — A long, narrow ridge of sand or shingle extending from the coast into the sea or across a river mouth. Forms by longshore drift depositing material beyond a headland or change in coastline direction. Example: Spurn Head, UK.

What is glacial erosion and its two main processes? — Plucking: Meltwater freezes around rock fragments, which are pulled away as the glacier moves. Abrasion: Rock fragments embedded in the glacier's base scratch and grind the valley floor, smoothing it.

What is a U-shaped valley and how does it form? — A wide, flat-bottomed, steep-sided valley formed by a glacier. Glaciers erode by plucking and abrasion, transforming a V-shaped river valley into a U-shape. Example: Yosemite Valley, USA.

What are the three types of weathering? — Physical (mechanical): Rock broken without chemical change (e.g., freeze-thaw, thermal expansion). Chemical: Rock altered by chemical reactions (e.g., carbonation dissolving limestone). Biological: Organisms break down rock (e.g., tree roots, lichens).

What is freeze-thaw weathering? — Water enters cracks in rock and freezes, expanding by ~9%, widening the crack. Repeated freezing and thawing progressively breaks the rock into angular fragments (scree). Common in mountain and periglacial environments.

What is a fjord? — A long, narrow, deep inlet carved by a glacier that has since retreated and been flooded by the sea. Characterized by steep cliff walls. Famous examples in Norway, New Zealand (Milford Sound), and Chile.

What is mass movement? — The downhill movement of rock, soil, or debris under gravity. Types include: rockfall (free fall), landslide (sliding along a plane), slump (rotational sliding), mudflow (fluid movement of saturated debris).

What is a tipping point in physical geography? — A threshold beyond which a system rapidly shifts to a new state that may be difficult to reverse. Example: Arctic ice melting reduces albedo, causing more warming — a positive feedback loop.

What is the drainage basin / catchment area? — All the land that drains into a particular river system. Separated from adjacent drainage basins by a watershed (ridge of high land). Includes the river and all its tributaries.