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EnglandGeology

The Earth and its history

5 dot points across 5 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do geologists work out the order and the age of rocks and events?

Geochronological principles let geologists order events and estimate ages: the law of superposition (in undisturbed strata the oldest is at the base), the principle of cross-cutting relationships (a feature that cuts another is younger), the use of fossils to correlate rocks of the same age, and the idea of half-life, which gives the absolute age of a rock in years from radioactive decay; relative dating gives the order of events, absolute dating gives the age in years.
A focused answer to the Eduqas GCSE Geology statement on dating rocks. Covers relative dating (the law of superposition, cross-cutting relationships and fossil correlation), absolute dating using the idea of half-life, and how a sequence of events is read from a section.
14 min answer →

How do rocks record past changes in climate and sea level?

The rock record preserves evidence of past climate and sea-level change: rock types act as climate indicators (coal for warm wet swamps, evaporites for hot arid conditions, tillite for cold glacial conditions, reef limestone for warm shallow seas); rising sea level (transgression) gives a fining-upward, deepening sequence and falling sea level (regression) a coarsening-upward sequence; these changes are driven by ice ages, plate movement and changes in the volume of the ocean basins.
A focused answer to the Eduqas GCSE Geology statement on past climate and sea level. Covers rock types as climate indicators (coal, evaporites, tillite, reef limestone), transgression and regression and the sequences they leave, and the causes of sea-level change.
13 min answer →

What does the fossil record tell us about the origin and development of life?

The fossil record shows that life began early and became more complex and diverse over geological time; major milestones include the first simple cells, the Cambrian appearance of abundant shelly animals, the move of life onto land, and the rise and fall of major groups; evolution by natural selection explains the changes, fossils provide the evidence, and mass extinctions repeatedly reset the course of life (for example the end-Permian and end-Cretaceous events).
A focused answer to the Eduqas GCSE Geology statement on the history of life. Covers how the fossil record shows life becoming more complex over time, the major milestones, evolution by natural selection as the explanation, and the role of mass extinctions in resetting life.
13 min answer →

What evidence shows that the Earth's surface is made of moving plates?

The Earth's outer layer is divided into tectonic plates that move slowly over the mantle, driven by convection; the evidence for plate tectonics includes the fit of the continents, matching fossils and rock sequences across oceans, and the symmetrical magnetic stripes of the sea floor; plates meet at constructive (divergent), destructive (convergent) and conservative (transform) margins, each with characteristic earthquakes, volcanoes and landforms.
A focused answer to the Eduqas GCSE Geology statement on plate tectonics. Covers tectonic plates and the convection that drives them, the evidence (continental fit, matching fossils and rocks, magnetic stripes and sea-floor spreading), and the three types of plate margin with their earthquakes, volcanoes and landforms.
14 min answer →

How does the rock cycle link the three rock families through one continuous set of processes?

The rock cycle links igneous, sedimentary and metamorphic rocks through the processes of weathering, erosion, transport, deposition, burial and lithification, melting and crystallisation, and metamorphism; the cycle is driven by energy from the Sun (at the surface) and from the Earth's interior (at depth), and any rock can be changed into any other given time and the right conditions.
A focused answer to the Eduqas GCSE Geology statement on the rock cycle. Covers the three rock families and the processes that connect them (weathering, erosion, transport, deposition, lithification, melting, crystallisation and metamorphism), the two energy sources that drive the cycle, and how any rock can become any other.
13 min answer →