Science
Earth & Space Science
Rocks, plate tectonics, water, weather and climate, out to the solar system and stars.
- 10 chapters
- 30 lessons
- 30 visual guides
- All free
Chapters
Earth as a System (Free preview)
Explore earth as a system through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 1.1Earth’s spheresEarth works like connected rooms in one house. Water, air, rocks, and living things exchange material and energy across their boundaries.Visual guide
- 1.2Cycles and interactionsA cycle follows matter on a returning journey. Energy powers many of those journeys, but energy and matter do not behave in the same way.Visual guide
- 1.3Reading Earth science dataEarth data are clues. Before comparing two numbers, check their units, locations, time intervals, and how the measurements were made.Visual guide
Earth Materials
Explore earth materials through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 2.1MineralsMinerals are naturally made building materials with organized atoms. Color is one clue, but several tests together identify a mineral more reliably.Visual guide
- 2.2Rock typesA rock records how its ingredients were assembled. Cooling, accumulation, and changes under heat or pressure leave different kinds of clues.Visual guide
- 2.3The rock cycleThe rock cycle is a network of possible routes, not a conveyor belt that every rock follows in order.Visual guide
Plate Tectonics
Explore plate tectonics through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 3.1Evidence for moving platesMoving plates were discovered by fitting many clues together. A coastline match alone is weaker evidence than patterns that agree across rocks and oceans.Visual guide
- 3.2Plate boundariesA plate boundary is a meeting place with different traffic rules. Plates can separate, collide, or slide past each other.Visual guide
- 3.3Earthquakes and volcanoesEarthquakes release stored strain suddenly. Volcanoes bring molten material upward. Their maps reveal patterns, but a pattern cannot give an exact eruption or earthquake date.Visual guide
Earth’s Surface
Explore earth’s surface through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 4.1WeatheringWeathering breaks or changes material where it is. Erosion carries the resulting material away, so the two processes should not be confused.Visual guide
- 4.2Erosion and depositionMoving water, wind, ice, and gravity sort and carry sediment. A carrier often drops material when its ability to move it decreases.Visual guide
- 4.3Landscapes over timeA landscape is the result of construction and removal acting over time. Today's shape may record conditions that no longer exist.Visual guide
Geologic History
Explore geologic history through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 5.1Relative datingRelative dating puts events in order without necessarily assigning calendar ages. It is like deciding which page came first before learning when the book was printed.Visual guide
- 5.2FossilsFossils are selected traces of past life, not a complete video of every organism. Preservation conditions shape the record we can study.Visual guide
- 5.3Absolute dating and geologic timeRadiometric dating uses predictable changes in atoms. It works only when the sample, isotope system, and history are appropriate for the question.Visual guide
Water on Earth
Explore water on earth through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 6.1The water cycleThe water cycle has many routes and storage places. A drop can take a quick trip through a stream or a very slow trip underground.Visual guide
- 6.2GroundwaterGroundwater fills connected spaces below the surface. It is usually water in pores and fractures, not a giant underground river.Visual guide
- 6.3Oceans and currentsThe ocean moves heat and dissolved material around the planet. Surface winds and differences in water density influence different parts of this circulation.Visual guide
Weather
Explore weather through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 7.1The atmosphereThe atmosphere has layers, but air keeps moving between regions. Pressure, temperature, and moisture help explain those movements.Visual guide
- 7.2Air masses and frontsAn air mass carries a regional combination of temperature and moisture. A front is the boundary where contrasting air masses meet.Visual guide
- 7.3Interpreting weather mapsA weather map combines measurements into a picture. A forecast describes likely future conditions, with uncertainty that usually grows farther ahead.Visual guide
Climate
Explore climate through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 8.1Climate driversClimate depends on how energy enters, moves through, and leaves Earth. Several controls interact, so latitude alone cannot explain every local climate.Visual guide
- 8.2Climate recordsClimate records combine direct measurements with natural archives. Different archives capture different places, seasons, and time spans.Visual guide
- 8.3Human influences and uncertaintyTo explain climate change, scientists compare possible causes with measured patterns and physical mechanisms. Uncertainty about details does not erase evidence about broad causes.Visual guide
The Solar System
Explore the solar system through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 9.1Gravity and orbitsAn orbit is continuous falling around another body. Gravity changes the direction of motion while inertia keeps the object moving.Visual guide
- 9.2Planets and smaller bodiesSolar-system objects differ in composition, history, and orbit. Classification helps organize those differences without implying every member is identical.Visual guide
- 9.3Earth–Moon–Sun interactionsThe Moon is always partly lit by the Sun. We see different portions of that lit half as its position changes around Earth.Visual guide
Stars and the Universe
Explore stars and the universe through explanations, original examples, concept flashcards, and section-linked practice.
3 lessons
- 10.1StarlightStarlight is a message carried by electromagnetic waves. Its brightness, colors, and spectral lines reveal different properties and must be interpreted carefully.Visual guide
- 10.2Stellar life cyclesStars change as gravity and energy production compete. Their starting mass strongly influences their lifetime and eventual fate.Visual guide
- 10.3Galaxies and the expanding universeThe universe contains galaxies separated by enormous distances. Expansion describes changing large-scale distances, not an explosion from a special location inside space.Visual guide
