Grade 10 Geography – Rocks Quiz
1. Which of the following is the main rock type formed by cooling and solidification of magma or lava?
Igneous rocks form when molten material (magma or lava) cools and solidifies. Sedimentary rocks form from deposited particles, metamorphic rocks from alteration of existing rocks, and 'organic rock' is not a primary geological category.
2. What process primarily transforms sediment into sedimentary rock?
Lithification involves compaction of loose sediments and cementation by minerals, turning them into sedimentary rock. Melting produces igneous rocks, metamorphism alters rocks under heat and pressure, and biological activity alone does not form most sedimentary rocks.
3. Which Kenyan landmark is formed mainly of intrusive igneous rock (granite)?
Mount Kenya is the eroded core of an ancient volcano composed largely of intrusive igneous rocks such as granite. The other options are dominated by sediments or coral-derived deposits.
4. Which type of weathering involves the breakdown of rock by physical forces like temperature changes and freeze–thaw?
Mechanical weathering breaks rocks into smaller pieces through physical forces (e.g., thermal expansion, freeze–thaw). Chemical weathering alters rock minerals; biological cementation and solution deposition are not types of physical breakdown.
5. Which rock texture indicates rapid cooling of lava at the Earth's surface and usually small crystals?
Aphanitic texture is fine-grained, indicating rapid cooling of lava at or near the surface so crystals are too small to see. Phaneritic is coarse-grained (slow cooling), foliated relates to metamorphic rocks, and clastic describes sedimentary grains.
6. Which of these Kenyan resources is commonly associated with coastal heavy mineral sands?
Kenya's coastal beaches (e.g., Kwale area) contain heavy mineral sands rich in ilmenite and zircon. Coal is not typical there, basalt is volcanic, and marble is metamorphic.
7. What is the primary agent that transports sediments down the slopes of the Kenyan highlands into the Rift Valley rivers?
Running water from rain and rivers erodes and transports sediments from highlands into rivers and the Rift Valley. Kenya has no extensive modern glaciers; wind transports some sediments but rivers are the main agent; tectonic uplift does not transport sediments.
8. Which process best explains the formation of limestone found along parts of the Kenyan coast?
Limestone commonly forms from accumulated calcium carbonate from shells and corals in shallow marine settings like the Kenyan coast. Lava solidification produces igneous rock, metamorphism of sandstone yields quartzite, and volcanic ash deposition forms tuff.
9. Which statement about metamorphic rocks is correct?
Metamorphic rocks originate when existing rocks are altered by heat and pressure (and chemically active fluids) without melting. Melting would create igneous rocks; porosity varies; biological activity is not the cause.
10. Which sedimentary structure indicates past flow direction of water, commonly found in river deposits?
Cross-bedding forms when sediments are deposited by currents or wind and shows the direction of flow. Columnar jointing is igneous cooling feature, vesicular texture is volcanic, and gneissic banding is metamorphic.
11. Which mineral is most resistant to chemical weathering and commonly abundant in sand and sedimentary rocks?
Quartz is chemically stable and resistant to weathering, so it accumulates in sands and sediments. Feldspar weathers more easily to clays, calcite dissolves in acidic conditions, and biotite is a weatherable mica.
12. What is foliation in metamorphic rocks?
Foliation is the alignment of platy or elongated minerals under directed pressure during metamorphism, producing layers or bands. The other options describe vesicles, clastic sedimentary texture, and igneous cooling textures.
13. Which rock type typically contains fossils?
Fossils are usually preserved in sedimentary rocks because organisms are buried in sediments. Igneous rocks form from molten material that destroys organic remains; metamorphism often destroys fossils; obsidian is a volcanic glass (igneous).
14. What term describes the ability of a rock to allow water to pass through it?
Permeability is the property that measures how easily fluids can flow through connected pore spaces in a rock. Hardness measures resistance to scratching, grain size is a textural feature, and malleability is a metal property.
15. Which of these is an example of chemical weathering?
Chemical weathering includes reactions like dissolution where acids in rainwater dissolve minerals such as calcite in limestone. Frost shattering, abrasion, and root action are mechanical/physical or biological processes.
16. Which process forms metamorphic rocks by heating from nearby magma without large-scale pressure?
Contact metamorphism occurs where rocks are heated by an intruding magma body, changing them locally without the large pressures of regional metamorphism. Hydrolysis is a chemical weathering reaction; diagenesis is low-grade alteration of sediments into rock.
17. Which layer of the rock cycle is responsible for creating sediments through breaking down of rocks at the Earth's surface?
Weathering (breaking down) and erosion (transport) at the Earth's surface produce sediments. Solidification/crystallization form igneous rocks, and metamorphism alters rocks under heat and pressure.
18. Which rock would you expect to find as a building stone because of its hardness and resistance to weathering in Kenya?
Granite is hard, durable, and resistant to weathering, making it a common building and paving stone in many parts of Kenya. Shale is weak and splits easily; peat and unconsolidated sand are unsuitable as building stones.
19. Which term describes sediments laid down at the mouth of a river where it meets the sea, commonly forming flat land of deposited material?
A delta forms where a river deposits sediments faster than the sea can remove them, building out a deposit at the river mouth. Moraines are glacial deposits, buttes are isolated hills, and dunes are wind-blown sand accumulations.
20. How does particle size of sediments relate to the energy of the transporting medium?
Fast-moving water or strong currents have enough energy to transport coarse materials like gravel, while slow-moving water deposits finer particles like silt and clay. Energy directly affects transport capacity.
21. Which dating method gives an absolute age in years for igneous rocks and some metamorphic rocks?
Radiometric dating measures decay of radioactive isotopes to give absolute ages. Stratigraphic superposition and fossil correlation provide relative ages; color comparison is not a dating method.
22. Which rock characteristic is most useful to distinguish between intrusive and extrusive igneous rocks in the field?
Intrusive igneous rocks cool slowly underground and develop coarse, visible crystals; extrusive rocks cool quickly at the surface and have fine-grained or glassy textures. Color may vary; fossils are absent in igneous rocks; magnetic properties vary but are not primary distinction.
23. What causes the banding seen in gneiss, a high-grade metamorphic rock?
Gneissic banding forms when minerals separate into light and dark layers during high-grade metamorphism under directed pressure and heat. The other options describe sedimentary or volcanic origins.
24. Which soil-forming process is most directly linked to the breakdown of parent rock into smaller mineral particles?
Weathering (both physical and chemical) breaks down parent rock into mineral particles that contribute to soil formation. Transpiration, compaction, and irrigation affect soil moisture or structure but are not the primary breakdown processes.
25. Which of these is a typical indicator that a sedimentary rock formed in a shallow marine environment?
Shallow marine sediments often preserve marine fossils and form well-sorted sands, limestones, or shelly deposits. Columnar jointing is volcanic, foliation is metamorphic, and glacial striations indicate ice activity.
26. What feature would you expect in an extrusive igneous rock like basalt that cooled quickly at the surface?
Rapid cooling at the surface produces fine-grained textures; gases escaping during eruption create vesicles. Large crystals form in slow-cooling intrusive rocks, foliation is metamorphic, and rounded detrital grains describe sedimentary rocks.