Evidence chain
Source-based Earth science
Read the rocks. Follow the evidence.
Understand how Earth works by tracing the rocks, fossils, maps and measurements behind the conclusion.
Choose a geology question
Six lessons are grouped by the kind of question they answer: dating evidence, competing explanations, or the history of geological knowledge.
Dating rocks and Earth
See how relative sequences and radiometric clocks answer different age questions.
Worked methods lesson
How Fossils Help Geologists Date Rocks
Work through fossil correlation, numerical anchors and common failure modes.Theories and processes
Compare explanations by what they claim, what they predict and which observations test them.
Theory comparison
Continental Drift vs Plate Tectonics: What Changed?
Compare what moves, what happens to ocean floor and how the models are tested.Concept correction
Uniformitarianism, Catastrophism, and Actualism Explained
See why modern actualism allows gradual change and rare catastrophes.History and maps
Trace how observations, definitions and institutions shaped geological knowledge.
History of ideas and evidence
The History of Geology: How Scientists Learned to Read Earth's Deep History
Trace how field evidence, instruments, institutions and theories changed.Map evidence comparison
What Was the First Geological Map?
Compare definition-dependent first-map claims using explicit criteria.Evidence method
How geologists build an explanation
Start with the answer#
Each lesson opens with a concise answer, then shows how rocks, fossils, maps or measurements support it. Diagrams and worked examples make relationships visible, while citations lead to the sources behind material claims.
Trace the reasoning#
Separate what was observed from what was inferred. When two explanations compete, compare what each claims, what it predicts and which evidence could show it is incomplete.
Know where the answer stops#
A teaching model is labeled as an illustration, and a historical belief is distinguished from a current explanation. Before moving on, identify one limitation or independent check. You do not need to finish every lesson to resolve one question.
Test your understanding
Can two different rocks tell the same story?
Match fossil ranges across two rock columns. See what the evidence tells you, and what it cannot establish on its own.
Try the fossil self-check →