Earth Science

Earth Science — General Science (ASVAB) Earth science questions appear regularly in the General Science (GS) subtest, which contributes directly to critical line scores for technical military jobs in the Army, Navy, Air Force, and beyond — so a solid grounding in Earth's structure, atmosphere, and natural cycles can meaningfully boost your score. --- ## Overview of Earth's Structure The Earth is organized into distinct layers, each with different compositions and properties. | Layer | Description | |-------|-------------| | Crust | Outermost, thin, rocky shell; where we live; divided into continental and oceanic crust | | Mantle | Thick layer of semi-molten rock (magma) beneath the crust; site of convection currents | | Outer Core | Liquid iron and nickel; generates Earth's magnetic field | | Inner Core | Solid iron and nickel; extremely high pressure and temperature | Plate tectonics is the theory that Earth's crust is broken into large sections called tectonic plates that move slowly over the mantle. This movement causes: - Earthquakes — sudden release of energy along faults (cracks in the crust) - Volcanoes — openings where magma reaches the surface and becomes lava - Mountain building — where plates collide (convergent boundaries) - Seafloor spreading — where plates pull apart (divergent boundaries) --- ## Rocks and the Rock Cycle All rocks fall into one of three categories, and they continuously transform from one type to another through the rock cycle. | Rock Type | How It Forms | Example | |-----------|-------------|---------| | Igneous | Cooled magma or lava | Granite, Basalt | | Sedimentary | Compressed layers of sediment | Limestone, Sandstone | | Metamorphic | Existing rock changed by heat/pressure | Marble,…