Internal Geological Processes: Volcanoes and Earthquakes
Internal Geological Processes
Internal geological processes are caused by the heat inside the Earth. These include volcanic activity, earthquakes, and the formation of ridges. The heat inside the Earth not only causes volcanic activity but also the movements of lithospheric plates that produce earthquakes and cause the great ranges.
Volcanoes
Definition
Volcanoes are often steep, conical mountains. However, not all volcanoes are high mountains or perfect cones. They are often under the sea, and their external appearance is that of a long crack.
Eruptions
Along with the liquid fraction, magma often contains solid materials, either because they have not melted or because they have solidified. Moreover, gas has always played a key role in the eruption. Most of the magma originates in shallow areas.
Volcano Structure
A typical volcano has the following parts:
- Crater
- Chimney
- Volcanic cone
- Magma chamber
- Side cones
Volcanic Terms
Active Volcanoes
Active volcanoes are those that are erupting or have erupted, although rest periods tend to occur that are more or less long. Currently, all volcanoes that have erupted in the last 25,000 years are considered active. Excluding intense submarine activity, there are over 600 active volcanoes.
Magma
Magma is the molten material in the deep Earth. Along with the liquid fraction, magma usually contains gases and solids.
Lava Flows
Lava flows are more or less slow-moving currents of molten lava flowing from the mouth of the volcano.
Pyroclasts
Pyroclasts are solid materials projected into the air by the violent escape of gases.
Types of Volcanic Activity
Several factors characterize volcanic activity:
- Gas Content: The accumulation of gases in the magma chamber or ducts increases the explosiveness of volcanic activity.
- Shape and Characteristics of the Volcanic Edifice: If the volcano has a deep, narrow chimney that is plugged, gases will accumulate and cause explosions.
- Viscosity of the Lava: The viscosity of a liquid is its resistance to flow. It is influenced by:
- The composition of the lava
- Temperature
- The content of solid materials
Earthquakes
Definition
An earthquake is a ground vibration caused by a sudden release of energy.
How Earthquakes Occur
Earthquakes occur when masses of rock break, or when a broken mass moves in relation to another.
Earthquake Terms
Fault
A fault is a fracture where large masses of rock break and move relative to each other.
Hypocenter
The hypocenter is the point within the Earth where the earthquake rupture starts. From here, vibrations, or seismic waves, are transmitted in all directions.
Epicenter
The epicenter is the point on the Earth’s surface directly above the hypocenter.
Magnitude
Magnitude is the amount of energy released by an earthquake.
Tsunamis
Tsunamis are huge waves caused by the sudden rise of a large body of water at the bottom of the sea. Most tsunamis are caused by earthquakes whose epicenter is beneath the sea, but they can also be caused by volcanic eruptions, submarine landslides, or even meteor impacts.
Lithosphere and Lithospheric Plates
Definition of lithosphere and lithospheric plates is missing from the original text. Boundaries between plates are marked by areas of intense geological activity, such as earthquakes, volcanic eruptions, and mountain formation.