Rocks: Types, Formation and Rock Cycle

The earth’s crust is made of rocks that may be hard or soft and have varied colours. The word rock has different meanings to different people. For example, an engineered rock is a material which can be blasted to make dames, roads and so on; a builder equates it with a hard-resistant building material.

Similarly, a layman can imagine rocks as pebbles on the beach. However, geologists define a rock as a collection of mineral grains (Alam and Mohammad, 2008).

Based on the mode of formation, rocks may be grouped into three families. These are as follows:

Igneous Rocks- Click to Read

Sedimentary Rocks- Click to Read

Metamorphic Rocks- Click to Read

Rock Cycle

The cycle starts with molten materials like magma, which comes from below the earth’s surface and reaches it subsequently. Magma occasionally erupts with the help of a weak surface or fracture and high interior pressure. Eruption results in lava after cooling and solidifying of magma. This process is called crystallization which can occur both beneath the earth’s surface and over the earth’s surface. The resultant rocks are called igneous rocks.

These rocks begin to be eroded when they are influenced by erosional agents like water, wind, glacier etc.; subsequently, hard rocks decompose and disintegrate slowly. The loose particles move downslope from one place to another with the help of erosional agents and deposited depressions, including oceans, river flood plains, swamps, desert basins etc. Sediments become sedimentary rocks under the lithification process.

If sedimentary rocks are involved in mountain building, these rocks have to face great pressure and heat, resulting in metamorphic rocks. The resultant rocks may face either more heat or erosional agents that can produce magma or sediments, respectively, and automatically, the cycle can start again.

Read More in Geomorphology

1. Earth Movements: Meaning and Types
2. Epeirogenic Earth Movements
3. Orogenic Earth Movements
4. Cymatogenic Earth Movements
5. Concept of Stress and Strain in Rocks
6. Folds in Geography
7. Fault in Geography
8. Mountain Building Process
9. Morphogenetic Regions
10. Isostasy: Concept of Airy, Pratt, Hayford & Bowie and Jolly
11. Continental Drift Theory of Alfred Lothar Wegener (1912)
12. Plate Tectonics: Assumptions, Evidences, Plate Boundaries and Features Formed
13. Volcanoes: Process, Products, Types, Landforms and Distribution
14. Earthquakes: Processes, Causes and Measurement
15. Plate Tectonics and Earthquakes
16. Composition and Structure of Earth’s Interior
17. Artificial Sources to Study Earth’s Interior
18. Natural Sources to Study Earth’s Interior
19. Internal Structure of Earth
20. Chemical Composition and Layering of Earth
21. Weathering: Definition and Types
22. Mass Wasting: Concept, Factors and Types
23. Models of Slope Development: Davis, Penck, King, Wood and Strahler
24. Davis Model of Cycle of Erosion
25. Penck’s Model of Slope Development
26. King’s Model of Slope Development
27. Alan Wood’s Model of Slope Evolution
28. Strahler’s Model of Slope Development
29. Development of Slope
30. Elements of Slope
31. Interruptions to Normal Cycle of Erosion
32. Channel Morphology and Classification
33. Drainage System and Drainage Pattern
34. River Capture or Stream Capture
35. Stream Channel Pattern
36. Fluvial Processes and Landforms: Erosional & Depositional
37. Delta: Definition, Formation and Types
38. Aeolian Processes and Landforms: Erosional & Depositional
39. Desertification: Definition, Problem and Prevention
40. Glacier: Definition, Types and Glaciated Areas
41. Glacial Landforms: Erosional and Depositional
42. Periglacial: Meaning, Processes and Landforms
43. Karst Landforms: Erosional and Depositional
44. Karst Cycle of Erosion
45. Coastal Processes: Waves, Tides, Currents and Winds
46. Coastal Landforms: Erosional and Depositional
47. Rocks: Types, Formation and Rock Cycle
48. Igneous Rocks: Meaning, Types and Formation
49. Sedimentary Rocks: Meaning, Types and Formation
50. Metamorphic Rocks: Types, Formation and Metamorphism
51. Morphometric Analysis of River Basins
52. Soil Erosion: Meaning, Types and Factors
53. Urban Geomorphology: Concept and Significance
54. Hydrogeomorphology: Concept, Fundamentals and Applications
55. Economic Geomorphology: Concept and Significance
56. Geomorphic Hazard- Earthquake: Concept, Causes and Measurement
57. Geomorphic Hazard- Tsunami: Meaning and Causes
58. Geomorphic Hazard- Landslides: Concept, Types and Causes
59. Geomorphic Hazard- Avalanches: Definition, Types and Factors
60. Integrated Coastal Zone Management: Concept, Objectives, Principles and Issues
61. Watershed: Definition, Delineation and Characteristics
62. Watershed Management: Objective, Practice and Monitoring
63. Applied Geomorphology: Concept and Applications