Earth Sciences Cheat Sheet
The core ideas of Earth Sciences distilled into a single, scannable reference — perfect for review or quick lookup.
Quick Reference
Plate Tectonics
The theory that Earth's outer shell (lithosphere) is divided into several rigid plates that move, float, and interact on the semi-fluid asthenosphere beneath them. Plate interactions at boundaries produce earthquakes, volcanoes, mountain ranges, and ocean trenches.
The Rock Cycle
The continuous process by which rocks are created, transformed, and recycled among the three major rock types: igneous (formed from cooling magma), sedimentary (formed from compacted sediments), and metamorphic (formed under heat and pressure). No rock type is permanent; given enough time and the right conditions, any rock can become any other type.
Geologic Time Scale
The chronological framework dividing Earth's 4.6-billion-year history into hierarchical units: eons, eras, periods, and epochs. It is based on stratigraphy, fossil succession, and radiometric dating, and provides the context for understanding the sequence and timing of geologic and evolutionary events.
Weathering and Erosion
Weathering is the in-place breakdown of rocks by physical (frost wedging, thermal expansion), chemical (dissolution, oxidation), or biological processes. Erosion is the transport of weathered material by water, wind, ice, or gravity. Together, they reshape landscapes and produce sediment.
Earth's Interior Structure
Earth is composed of concentric layers differentiated by composition and physical properties: a thin silicate crust, a thick silicate mantle, a liquid iron-nickel outer core, and a solid iron-nickel inner core. Seismic waves from earthquakes are the primary tool used to infer the properties of these layers.
The Water Cycle (Hydrologic Cycle)
The continuous movement of water through the Earth system via evaporation, transpiration, condensation, precipitation, infiltration, surface runoff, and groundwater flow. It links the atmosphere, hydrosphere, lithosphere, and biosphere and is driven primarily by solar energy and gravity.
Seismology and Earthquakes
Seismology is the study of seismic waves generated by earthquakes, explosions, and other sources. Earthquakes occur when accumulated stress along faults exceeds the frictional strength of the rock, causing sudden rupture and energy release. Magnitude scales (e.g., moment magnitude) quantify the energy released.
Volcanism
The process by which molten rock (magma), gases, and ash are expelled from Earth's interior to the surface. Volcanic activity occurs predominantly at divergent plate boundaries, convergent plate boundaries (subduction zones), and hot spots. Eruption style depends on magma composition, viscosity, and gas content.
Climate System and Greenhouse Effect
Earth's climate system involves complex interactions among the atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere. The greenhouse effect occurs when atmospheric gases (CO2, methane, water vapor) absorb and re-emit infrared radiation, warming Earth's surface above what it would be without an atmosphere.
Stratigraphy and the Principle of Superposition
Stratigraphy is the study of rock layers (strata) and their relationships. The principle of superposition states that in an undisturbed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest at the top. This principle, along with cross-cutting relationships and fossil succession, allows geologists to determine relative ages of rocks.
Key Terms at a Glance
Get study tips in your inbox
We'll send you evidence-based study strategies and new cheat sheets as they're published.
We'll notify you about updates. No spam, unsubscribe anytime.