Earth's Internal Dynamics: Heat, Tectonics, and Seismic Risk

Earth's Internal Dynamics and Geothermal Heat

The increase in temperature from the Earth's surface inward is known as the Geothermal Gradient. The internal heat of the Earth originates from the impacts of meteors and giant mineral pieces (during planetary formation).

The Earth's Crust and Magma Formation

The crust is a layer of rocks with a thickness ranging from less than ten kilometers to more than seventy kilometers. Rocks that cannot withstand intense pressure can melt and form magma. Magma is a mixture of molten rock and gas found inside the crust. Lava is molten rock without gas that reaches the surface.

Volcanic Eruptions: States of Matter

During a volcanic eruption, materials are expelled in all three states:

• Gases: Including carbon dioxide and water vapor.
• Liquids: Lava.
• Solids (Pyroclasts): These are rock fragments released into the air.

Seismology: Understanding Earthquakes

Earthquakes are vibrations caused by sudden movements or breaks in the Earth's crust.

• The place where the breaking occurs is the Hypocenter.
• The Epicenter is the point on the surface where the earthquake is first felt with maximum intensity.

The Richter Scale indicates the quantity of energy released in the hypocenter. A seismograph is used to detect seismic waves.

Mantle Composition and Plate Structure

The mantle is primarily composed of peridotite. The crust itself has two main types:

• Continental Crust: Abundant in granite.
• Oceanic Crust: Composed mainly of basalt.

Plate Tectonics Theory

Oceanic and continental Lithospheric Plates are enormous mixed fragments into which the lithosphere is broken. This fragmentation is driven by Convection Currents (similar to heating water).

Types of Plate Movement

Convection currents cause plate movement in three primary ways:

1. Separating (Divergent)
2. Colliding (Convergent)
3. Sliding (Transform)

Plate Tectonics Theory is the mechanism that explains the causes and consequences of lithospheric plate movements. The thickening of the crust caused by the collision of continents gives rise to mountain chains, such as the Pyrenees or the Himalayas. Surface relief is formed either by the collision of lithospheric plates or by volcanic activity.

Geological Risk Management

Geological risk involves assessing the potential for natural hazards (earthquakes, eruptions) to cause damage.

Risk Management Measures

• Risk Assessment: The set of measures taken to evaluate the possibility that a risk will materialize and cause damage.
• Prevention: Measures taken so that damage is minimal if the risk materializes.
• Forecasting: Attempts to determine the time and place at which the risk will materialize in the form of an earthquake or volcanic eruption.

Isostatic Movements

Vertical movements are isostatic movements where the lithosphere tends to sink in some places and rise in others. Subsidence is the sinking vertical movement of the crust.