Power Of The Planet

What is the landform cycle?

A model explaining how landscapes change over time through erosion, moving through youth, maturity and old age.

What happens during the youthful stage of the landform cycle?

Rivers erode vertically, creating deep V-shaped valleys, steep slopes, waterfalls and rapids.

What happens during the mature stage of the landform cycle?

Valleys become wider, slopes become less steep and rivers erode both downwards and sideways.

What happens during the old age stage of the landform cycle?

Long periods of erosion wear down mountains and hills into a low, gently rolling landscape called a peneplain.

What are the four main layers of the Earth?

Crust, mantle, outer core and inner core.

What is the Earth's crust?

The thin, solid outer layer of Earth where continents and ocean floors are found.

What is the Earth's mantle?

A thick layer of hot rock beneath the crust. Movement within the mantle helps drive tectonic plate movement.

What is the Earth's outer core?

A layer of extremely hot, liquid iron and nickel surrounding the inner core.

What is the Earth's inner core?

The extremely hot, solid centre of Earth, made mainly of iron and nickel.

What is continental drift?

The theory that continents were once joined together in a supercontinent and have slowly moved apart over millions of years.

Who proposed the theory of continental drift?

Alfred Wegener, who proposed that the continents were once joined in a supercontinent called Pangaea.

What evidence supports continental drift?

Continents fit together like a jigsaw, matching fossils and rock formations occur on different continents, and ancient climate evidence supports their former positions.

What are convection currents?

Circular movements in the mantle caused by heat from Earth's interior. Hot material rises and cooler material sinks, helping move tectonic plates.

What are tectonic plates?

Huge sections of Earth's rigid outer shell that move slowly over the softer material beneath them.

What is the Pacific Ring of Fire?

A horseshoe-shaped zone around the Pacific Ocean with many volcanoes and earthquakes, mostly associated with tectonic plate boundaries and subduction.

What are the four main types of plate boundaries?

Constructive, destructive, collision and conservative boundaries.

What is a constructive plate boundary and what is an example?

Two plates move apart, allowing magma to rise and form new crust. Example: the Mid-Atlantic Ridge.

What is a destructive plate boundary and what is an example?

Two plates move together and one plate sinks beneath the other, destroying oceanic crust and often causing volcanoes and earthquakes. Example: the Nazca Plate sinking beneath the South American Plate near the Andes.

What is a collision plate boundary and what is an example?

Two continental plates move together, pushing and folding rock upwards to form mountains. Example: the Himalayas, formed by the Indian and Eurasian plates.

What is a conservative plate boundary and what is an example?

Two plates slide horizontally past each other, causing earthquakes without creating or destroying crust. Example: the San Andreas Fault in California.

Why do some geography courses teach three plate boundary types while others teach four?

Collision is often considered a type of convergent boundary. Some courses separate continental collision from destructive subduction boundaries.

What is a shield volcano?

A wide volcano with gentle slopes formed by fluid lava spreading over large distances. Example: Mauna Loa in Hawaii.

What is a cone volcano?

A cone-shaped volcano built up by repeated eruptions of lava and volcanic material. Example: Mount Ruapehu in New Zealand.

What is a caldera volcano?

A large basin-shaped depression formed when a volcano collapses after a major eruption empties part of its magma chamber. Example: the volcanic caldera beneath Lake Taupō.

What is a lava dome volcano?

A rounded, steep-sided mound formed when thick, sticky lava piles up around a volcanic vent. Example: lava domes at Mount St Helens in the USA.

What is folding?

The bending of rock layers caused by pressure in Earth's crust, often forming folds and mountain ranges.

What is faulting?

The cracking of Earth's crust and movement of rock along a fault due to forces acting on the crust.

How are earthquakes caused by tectonic plate movement?

Stress builds up in rocks as plates move. When the rocks suddenly slip along a fault, stored energy is released as seismic waves, shaking the ground.

What is weathering?

The breakdown of rock at or near Earth's surface without the material necessarily being moved away.

What is physical or mechanical weathering?

Rock breaks into smaller pieces without changing its chemical composition. Example: water freezes in cracks, expands and breaks the rock.

What is chemical weathering?

Rock is broken down through chemical reactions that change its minerals. Example: acidic rainwater dissolving limestone.

What is biological weathering?

Living organisms break down rock. Example: plant roots grow into cracks and gradually force them apart.

What is erosion?

The wearing away, removal and transportation of rock and soil by natural forces.

What are the main agents of erosion?

Running water, wind, glaciers and ice, waves and gravity.

How does water cause erosion?

Rivers and rain remove soil and rock, while moving water carries sediment downstream.

How does wind cause erosion?

Wind picks up and transports loose particles, which can wear down exposed rock and reshape land.

How do glaciers cause erosion?

Moving ice scrapes, grinds and plucks rock from the landscape, creating features such as U-shaped valleys.

How do waves cause erosion?

Waves wear away coastlines through the force of the water and rock fragments scraping against coastal cliffs.

How does gravity cause erosion?

Gravity pulls soil and rock downhill through processes such as landslides, rockfalls and slumping.

Where and when did the Christchurch earthquake occur?

It struck Christchurch and the surrounding Canterbury region on the east coast of New Zealand's South Island at 12:51 pm on