Key Terminology

Convection Currents:

The movement of molten rock in the mantle caused by heat from the Earth's core. These currents drive the movement of tectonic plates, influencing volcanic activity, earthquakes, and the formation of geological features.

Continental Drift:

The hypothesis that continents have moved across Earth’s surface over geological time. Proposed by Alfred Wegener, it suggests that continents were once joined in a supercontinent called Pangaea.

Earth’s Layers:

Earth's structure is divided into layers, each with distinct characteristics:

1. Crust: The outermost layer; solid and thin, composed of continental and oceanic crust.

2. Mantle: Lies beneath the crust; composed of semi-solid rock, where convection currents occur.

3. Outer Core: A liquid layer made of iron and nickel, responsible for Earth's magnetic field.

4. Inner Core: The innermost solid layer, composed of iron and nickel, extremely hot.

Earth’s Resources:

Natural materials such as minerals, fossil fuels, water, soil, and timber, which are used for human consumption and economic activities.

Earthquakes:

Sudden shaking of the Earth's surface caused by the release of energy along fault lines or from volcanic activity. They produce seismic waves and can cause significant damage.

Epicenter:

The point on Earth's surface directly above the earthquake’s focus, where seismic waves are most intense.

Fault Lines:

Fractures in Earth's crust where blocks of rock have moved relative to each other. They are often associated with seismic activity.

Faulting:

The fracturing of Earth’s crust when stress exceeds the rock's strength, causing displacement.

1. Normal Fault: The rock above the fault moves downward.

2. Slip Fault: The rock moves horizontally along the fault.

3. Reverse Fault: The rock above the fault moves upward.

Folding:

The bending of rock layers due to compressional forces, usually at convergent plate boundaries.

1. Anticlines: Upward-arching folds.

2. Synclines: Downward-arching folds.

Lithosphere:

The rigid outer layer of Earth, comprising the crust and upper mantle. It is divided into tectonic plates that float on the semi-fluid asthenosphere.

Magma vs. Lava:

• Magma: Molten rock beneath Earth's surface.

• Lava: Molten rock that reaches Earth’s surface during a volcanic eruption.

Magnetic Striping:

Patterns of magnetic fields recorded in the ocean floor's basalt. These patterns provide evidence of seafloor spreading and periodic reversals of Earth’s magnetic field.

Mercalli Scale:

A qualitative scale that measures the intensity of an earthquake based on observed effects and damage, ranging from I (not felt) to XII (total destruction).

Mountain Building:

The geological processes, such as plate collisions and volcanic activity, that create mountain ranges.

Pangaea:

A supercontinent that existed millions of years ago, composed of all Earth's continents joined together, as proposed by Wegener’s theory of continental drift.

Plate Boundaries:

Regions where tectonic plates interact:

1. Convergent: Plates move towards each other, forming mountains or subduction zones.

2. Divergent: Plates move apart, forming new crust at mid-ocean ridges.

3. Transform: Plates slide horizontally past each other, often causing earthquakes.

Plate Tectonics:

A scientific theory explaining the movement of Earth's lithospheric plates and their interactions, which shape Earth's surface and cause phenomena like earthquakes and volcanic eruptions.

Richter Scale:

A logarithmic scale that measures the magnitude (energy release) of earthquakes. Each increase of 1.0 represents a tenfold increase in amplitude.

Rift Valley:

A large elongated depression formed at divergent boundaries where tectonic plates move apart. Examples include the East African Rift.

Seafloor Spreading:

The process where new oceanic crust forms at mid-ocean ridges as tectonic plates move apart, pushing older crust outward.

Seismic Waves:

Energy waves generated by earthquakes. There are two main types:

1. P-waves (Primary waves): Travel fastest, compressing and expanding material.

2. S-waves (Secondary waves): Slower, move material perpendicular to wave direction.

Seismograph:

An instrument used to detect and record seismic waves produced by earthquakes.

Tectonic Plates:

Large, rigid pieces of Earth's lithosphere that move over the asthenosphere (semi-fluid upper mantle). Their movement causes geological events such as earthquakes, volcanic activity, and mountain formation.

Tsunami:

A large, powerful sea wave caused by underwater earthquakes, volcanic eruptions, or landslides. Tsunamis can cause extensive coastal damage.

Volcanoes:

Openings in Earth’s crust where magma, gases, and ash escape.

1. Stratovolcano: Tall, steep-sided, with explosive eruptions.

2. Shield Volcano: Broad, gently sloping, with fluid lava flows.

3. Cinder Cone Volcano: Small, steep-sided, formed from volcanic ash and debris.

Wegener’s Theory:

Alfred Wegener’s theory that Earth's continents were once a single landmass (Pangaea) and have since drifted apart due to tectonic plate movement.