Rocks and Earth Materials

The term 'igneous' comes from the Latin word 'ignis', which means 'fire'. This is highly appropriate because igneous rocks are formed from the cooling and solidification of hot, molten magma or lava.

When molten magma cools slowly deep inside the Earth's crust, it forms intrusive igneous rocks (such as granite). In contrast, magma that cools on the Earth's surface forms extrusive igneous rocks.

When molten magma reaches the Earth's surface (where it is called lava) and cools down rapidly, it forms extrusive igneous rocks, such as basalt. The prefix 'ex-' indicates that the cooling occurs on the exterior surface.

Igneous rocks are classified into two main types based on where the magma cools: intrusive igneous rocks (which cool slowly inside the Earth) and extrusive igneous rocks (which cool rapidly on the Earth's surface).

Igneous rocks are also called primary rocks because they are the first rocks to form from the cooling and solidification of molten magma. Other rock types (sedimentary and metamorphic) are ultimately derived from them.

Rocks are classified into three major groups based on how they are formed. Igneous rocks form from cooled magma, sedimentary rocks form from accumulated mineral particles, and metamorphic rocks form when existing rocks are changed by heat and pressure. The other options list specific rock types rather than the three primary categories.

A rock is defined as any naturally occurring solid mass of mineral or mineraloid matter that constitutes part of the Earth's crust. The crust itself is the layer containing these rocks, while the mantle and core lie much deeper inside the Earth.

The Earth's core has a radius of approximately 3500 km and experiences extreme temperatures and pressures. It is primarily composed of nickel (Ni) and iron (Fe), which is why it is commonly referred to as the NIFE layer. Therefore, all the given statements are correct.

The oceanic crust is relatively thin and is mainly composed of silica and magnesium. This composition leads to it being commonly referred to as 'sima' (Si for silica and Ma for magnesium). In contrast, the continental crust is rich in silica and alumina.

Geologically, the Earth is divided into three main compositional layers: the outermost thin crust, the thick silicate mantle beneath it, and the dense metallic core at the center.

Igneous rocks form from the cooling and solidification of molten rock, which is called magma when underground and lava when it erupts onto the Earth's surface.

Sedimentary rocks are formed by the gradual accumulation and compaction of mineral and organic particles over time, which gently buries and preserves organisms. Igneous and metamorphic rocks involve extreme heat and pressure that would typically destroy any fossil remains.

Shale is a fine-grained sedimentary rock formed from the compaction of silt and clay mineral particles. When subjected to heat and pressure, shale can metamorphose into slate, gneiss, or other metamorphic rocks. Marble is also metamorphic, formed from limestone.

A bolt of lightning can reach temperatures of around 30,000 Kelvin (about 53,000 degrees Fahrenheit), which is about five times hotter than the surface of the sun and significantly hotter than the Earth's core (around 6,000 degrees Celsius) or lava.

Earth's crust is the outermost solid shell of our planet and is composed of various types of solid rock, such as igneous, sedimentary, and metamorphic rocks. Magma is molten rock found beneath the crust, and water covers much of the crust but does not make up the crust itself.