Science 1st Q.

The lectures in Science for the 1st Q. As a 10th grade student.

Lithosphere

Outermost solid layer of the earth; consists of the crust and the uppermost part of the mantle.

Crust

It forms the lithosphere (which is broken into tectonic plates). It is composed of rocks (granite and basalt). The crust has two parts — continental and oceanic.

Continental Crust

Thicker (up to 70 KM) less dense, composed mainly of basaltic rocks rich in silica and aluminum.

Oceanic Crust

Thinner (about 5-10 KM), denser, composed mainly of basaltic rocks and formed at mid-ocean ridges.

Asthenosphere

The layer of the Earth's mantle located beneath the lithosphere, characterized by its semi-fluid properties and ability to flow, allowing tectonic plates to move. It extends from 100-140 KM. The ASTHENOSPHERE is hot enough for small portions of rock to partially melt — creating tiny pockets of magma.

Mantle

The thick layer of rock BETWEEN the crust and core. It makes up about 84% of earth's volume and plays a crucial role in the planet's dynamic. It extends about 30-2,900 KM below the surface. The mantle is composed mainly of SILICATE MATERIALS (olluine, pyroxene, and garnet) and is rich in iron, magnesium, and silicon. It has two types — Upper and Lower Mantle.

Convection Current

It is the heat from the core and radioactive decay drive slow circulation in the mantle — influencing plate tectonics.

Upper Mantle

It contains the asthenosphere and extends from about 30-410 KM to 660 KM below the surface. It allows the movement of tectonic plates through convection currents.

Lower Mantle

It is the HOTTER and under HIGH PRESSURE than the upper mantle and extends from 660 KM to 2,900 KM. It is composed of MINERALS (like bridgemanite and ferropericlase) — which are stable under extreme conditions. It contributes to mantle convection on a larger scale — influencing plate movements and heat transfer from the core to the surface.

Core

The innermost layer of the earth (a.k.a. earth’s center). It extends from 2,900 KM to 6,371 KM. Mainly composed of iron and nickel with smaller amounts of lighter elements (like sulfur and oxygen).

Outer Core

It generates the earth’s magnetic field (convection currents of liquid iron create ELECTROC CURRENTS — producing the GEOMAGNETIC FIELD). It extends from 2,900 KM to 5,150 KM, it is the only liquid layer among the layers of the earth. The high temperatures — 4,000°C to 5,000°C keep the outer core molten.

Inner Core

It acts as an ANCHOR for the magnetic field generated by the outer core. It extends from 5,150 KM to 6,371 KM and despite the high temperatures, immense pressure keeps the inner core solid. It also rotates slightly faster than the rest of the planet — influencing earth's magnetic field.