Earth's Internal Heat, Volcanoes, Earthquakes

Energy Inside the Earth

Temperature in the Earth's Interior

Although the surface is cold, scientists have calculated that at 2000 km depth, the temperature exceeds 2500 °C, and in the Earth's core at 6300 km, it is about 4500 °C.

Consequences of Heat Loss

The Earth radiates heat outwards as magma. Magma is formed by molten rock found at high temperatures. When it reaches the surface, it forms volcanoes.

Volcanoes

What are Volcanoes?

Volcanoes form when magma rises to the surface. During eruptions, explosions occur, which expel gas from the magma.

Materials Emitted by Volcanoes

In eruptions, volcanoes emit:

• GASES: Help the lava escape.
• LAVAS: Liquid rock ejected by volcanoes.
• Pyroclastic materials: These are classified as: bombs (reaching up to 30 cm), lapilli, and ash (very thin and light).

Where Volcanoes Form

Volcanoes form at:

• Where two plates separate and magma from the mantle rises, forming large reliefs called mid-ocean ridges. Examples include the volcanoes of Iceland and the Cape Verde Islands.
• In subduction zones where two plates converge and one sinks beneath the other into the mantle. Volcanoes like Krakatoa or Chimborazo have formed in these areas.

Earthquakes

What are Earthquakes?

Tremors and earthquakes are ground shaking events that usually last from a few seconds to a few minutes.

Why Earthquakes Occur

• Tectonic earthquakes are caused by ruptures or fractures in rock masses.
• Volcanic earthquakes are produced by the movement of magma or fluids beneath volcanoes.

Seismic Zones of the Earth

Most earthquakes occur at the boundaries between lithospheric plates:

• In subduction zones where two plates converge and one is subducted beneath the other.
• Along mid-ocean ridges as a result of divergent plate movements.
• Along major faults, such as the San Andreas Fault, where two plates slide laterally past each other.

Magmatic Rocks

Formation of Magmatic Rocks

• Plutonic Rocks: Plutonic rocks form when magma solidifies deep within the Earth. Generally, they occur as large masses called plutons.
• Subvolcanic rocks: These form when magma rises through fractures or cracks but solidifies beneath the surface, creating rock masses that can be thin or extensive.
• Volcanic rocks: These occur when magma reaches the surface (as lava) and solidifies, often forming layers or flows.

Metamorphic Rocks

What are Metamorphic Rocks?

Metamorphic rocks originate from other existing rocks that are transformed when subjected to high heat and pressure.

Metamorphism Process

Metamorphism occurs when rocks are buried deep underground, subjected to intense pressure, or affected by hot magma, exposing them to high temperatures and pressures.

Origin of Metamorphic Rocks

Metamorphic rocks originate from various parent rocks. For example, shale, schist, and gneiss often come from clays or mudstones; marble comes from limestone; and quartzite comes from sandstone. The specific metamorphic rock formed depends on the parent rock and the intensity of the metamorphism.