2.1 Rocks

• define a rock and a mineral
• classify rocks as igneous, sedimentary or metamorphic
• describe how each type of rock forms
• explain the significance of rocks to human activities

“How does one kind of rock become another?”

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1. What rocks are made of
   40 min · 2 practice tasks · quiz
   The difference between a rock and a mineral, and the three families of rock.
2. Rocks of Kenya and how they are dated
   40 min · 2 practice tasks · quiz
   Where each rock type is found in Kenya, how geologists put an age to rock, and why it matters.
3. Minerals that make rocks
   40 min · 1 practice tasks · quiz
   What a mineral is, how it differs from a rock, and the few minerals a Kenyan learner actually meets in granite and limestone.
4. Classifying rocks by how they form
   40 min · 1 practice tasks · quiz
   The three families are decided by origin, not by colour or hardness, and field clues must serve that rule.
5. How igneous rocks form
   40 min · 1 practice tasks · quiz
   Magma against lava, intrusive against extrusive, and why cooling place decides texture.
6. Granite and other intrusive rocks
   40 min · 1 practice tasks · quiz
   Coarse interlocking crystals, Kenyan basement granite, and why it makes good building and monument stone.
7. Volcanic rocks of the Rift and highlands
   40 min · 1 practice tasks · quiz
   Basalt, phonolite, tuff and pumice as Kenya's everyday extrusive rocks, from Mount Kenya to the Chyulu Hills.
8. Igneous texture and cooling rate
   40 min · 1 practice tasks · quiz
   Grain size as a cooling clock: granite coarse, basalt fine, pumice holey, obsidian glass.
9. How sedimentary rocks form
   40 min · 1 practice tasks · quiz
   Weathering, transport, deposition and lithification, from Kenyan highlands to coast and lake basins.
10. Clastic sedimentary rocks
    40 min · 1 practice tasks · quiz
    Conglomerate, sandstone and shale as grain-size cousins, and what grain size says about the water that dropped them.
11. Limestone, coral and diatomite
    40 min · 1 practice tasks · quiz
    Chemical and organic sedimentary rocks: Kenyan coastal limestone, coral, Athi River cement rock and Kariandusi diatomite.
12. Fossils in sedimentary rock
    40 min · 1 practice tasks · quiz
    Why remains survive in sediment, why they fail in magma, and why Koobi Fora and Olorgesailie sit where they sit.
13. How metamorphic rocks form
    40 min · 1 practice tasks · quiz
    Heat and pressure change existing rock without melting it; contact against regional metamorphism.
14. Marble, slate, quartzite and soapstone
    40 min · 1 practice tasks · quiz
    The metamorphic rocks Grade 10 must name, with Kenyan marble, gneiss and Kisii soapstone as the local set.
15. The rock cycle with Kenyan examples
    40 min · 1 practice tasks · quiz
    How one Kenyan rock becomes another: Rift lava to sediment to marble, and granite unroofed then weathered.
16. Identifying local rock samples
    40 min · 1 practice tasks · quiz
    A field routine: look, grain, layers, fossils, hardness, then family and a Kenyan name if you can.
17. Rocks as resources in Kenya
    40 min · 1 practice tasks · quiz
    Cement, ballast, carvings, soils, groundwater and gemstones - how rock type steers what people can do.
18. Quarrying, communities and conservation
    40 min · 1 practice tasks · quiz
    Benefits and costs of extracting Kenyan rock, and why rehabilitation and respect for neighbours are part of the geography.