Chapter 2: Shaping of The Earth's Surface Vocabulary Flashcards

Comprehensive vocabulary flashcards covering plate tectonics, internal Earth structure, weathering, erosion, river and glacial dynamics, landforms, and geological hazards from Chapter 2.

Plate Tectonics

The scientific theory explaining the movement of large pieces of the Earth's outer layer (tectonic plates) horizontally over the asthenosphere, causing phenomena such as earthquakes, volcanic activity, mountain formation, and ocean basin creation.

Pangaea

The single landmass in which all continents were once joined together before drifting apart, as proposed by Alfred Wegener in $1912$.

Seafloor Spreading Theory

The theory proposed by Harry Hess and Robert S. Dietz in the $1950\text{s}$ stating that new oceanic crust is formed at mid-ocean ridges due to volcanic activity as rising magma solidifies and pushes older crust away.

Convection Currents

Circular movements in the mantle driven by heat from the Earth's core, where hot material rises and cooler material sinks, driving the movement of tectonic plates above.

Lithosphere

The solid outer layer of the Earth, consisting of the crust and upper-most solid mantle, which is divided into large and small moving tectonic plates.

Asthenosphere

The semi-fluid layer of the Earth's mantle directly beneath the lithosphere over which tectonic plates move.

Interior of the Earth

The layered internal structure of the Earth, comprising the outer Crust, intermediate Mantle, and central Core (divided into liquid outer core and solid inner core).

Crust

The solid outer shell of the Earth that sustains life, with an average thickness varying from $5\,\text{km}$ to $40\,\text{km}$, being thicker under continents and thinner under oceans.

Mantle

The thick layer of rocks situated between the crust and the core, having an average thickness of about $2,900\,\text{km}$ and divided into upper and lower sections.

Mohorovicio Discontinuity

The boundary boundary that separates the Earth's crust from the mantle, named after a Yugoslav seismologist.

Outer Core

The liquid section of the Earth's metallic core, mainly composed of iron.

Inner Core

The solid innermost part of the Earth composed of nickel and iron, which behaves like a solid due to extremely high pressure despite high temperatures.

Rate of Subsurface Temperature Rise

The increase in temperature observed when descending beneath the Earth's surface, occurring at a rate of $1^\circ\text{C}$ for every $32\,\text{metres}$.

External Processes

Natural processes that take place gradually on the surface of the Earth, including weathering, erosion, and mass movements.

Weathering

The process by which rocks exposed on the surface of the Earth get broken into smaller pieces in situ (in the same place).

Physical Weathering

The mechanical disintegration of rocks into smaller pieces without any change in their chemical composition.

Exfoliation

The peeling off of outer rock layers caused by alternate expansion from daytime sun heating and contraction from nighttime cooling, common in granitic rocks.

Frost-Action

A physical weathering process in cold lands where water seeps into rock cracks, freezes and expands, and widens cracks until the rock breaks apart.

Chemical Weathering

The dissolution or breakdown of rock minerals due to chemical reactions with water or air, producing features like caverns and sinkholes in soluble rocks.

Biological Weathering

The breaking up of rocks caused by organisms, such as plant roots widening cracks or secreting acidic juices, and burrowing animals like rabbits and rats.

Erosion

The act of carrying away weathered rock particles from one place to another by agents such as rivers, rainwater, glaciers, waves, and winds.

Mass Movements

Movements caused by gravity pulling loose rock masses, soil, or debris downward along mountain slopes.

Landslide

A type of mass movement where dry soil and rock pieces move down a steep slope under their own weight.

Earth Flow

A mass movement occurring when water-saturated clay and silt move down a gentle slope.

Mud-Flow

A mass movement where water-saturated rock debris moves down channels on steep hillsides.

Denudation

The process of stripping or making the land bare through external agents such as rivers, rainwater, ice/glaciers, sea waves, and winds.

Gorge

A narrow valley with steep walls formed in the upper course when a river cuts through hard rock.

V-Shaped Valley

A river valley widened by lateral erosion, formed in areas of soft rock and heavy rainfall during a river's upper course.

Waterfall

A sudden descent of river water over a big vertical step in a river bed, such as Venezuela's Angel Falls at approximately $980\,\text{metres}$ high.

Rapids

River features where water continuously jumps and falls over a sloping, rocky bed without forming a single deep vertical fall; a series of these are called cascades.

Three Courses of a River

The three stages along a river's trajectory from origin to sea: Upper Course (Mountain Stage), Middle Course (Plain Stage), and Lower Course (Delta Stage).

Meanders

Big loops formed by a river swinging from side to side across a flat plain in its middle course.

Distributaries

Multiple branching channels into which a main river splits in its lower course before falling into the sea, forming fertile alluvial deltas.

Mountain Glaciers

Masses of ice that move slowly down mountain tops along valleys, eroding V-shaped valleys into U-shaped valleys and melting to feed rivers.

Continental Glaciers

Large, thick ice sheets covering thousands of square kilometers of entire land surfaces, occurring primarily in Polar Regions.

Fold Mountains

Mountains formed by internal Earth movements causing crustal folding during cooling and contraction, such as the Himalayas, Alps, Appalachians, and Ural Mountains.

Block Mountains

Mountains formed when large masses of land break and are displaced vertically, as seen in the Vosges mountains and Rhine valley.

Volcanic Mountains

Mountains constructed by volcanic eruptions and material accumulation, such as Mt. Kilimanjaro in Africa and Mount Fujiyama in Japan.

Plateau

A broad, elevated stretch of land with a relatively level surface that rises sharply above surrounding lowlands, also known as a tableland.

Plain

A relatively flat and low-lying vast expanse of land, commonly formed by fertile deposits of silt, sand, and stones carried by major rivers.

Earthquake

A sudden shaking of the Earth's surface caused by interior instability and the rapid release of energy along tectonic boundaries.

Avalanche

A rapid and sudden flow of snow, ice, and rocks down a mountain slope in snow-covered mountain regions.

Glacial Lake Outburst Flood (GLOF)

A sudden and massive discharge of water from a glacial lake when a natural dam of ice or moraine debris breaks.

Dust Storm

A severe environmental hazard where strong winds lift large quantities of dust and sand from dry, bare soil into the air, reducing visibility and causing health risks.