11 formation of rock layers

Powerpoint for Earth and Life Science - Formation of Rock Layers

1. FORMATION OF ROCK LAYERS Prepared by: Engr. Ariel S. Motas Engr. Andreana Amor M. Gulay

2. LESSON 1: ROCK LAYERS - How are rock layers formed ? Stratified Rocks Also known as derivatives rock, maybe fragmental or crystalline. These rocks are product of SEDIMENTARY PROCESSES. These are made of visible layers of sediments. Formation on rock layers depend on its stratigraphy and stratification Stratigraphy It is the branch of geology that deals with the description, correlation, and interpretation of stratified rocks on and within the Earth. Stratification It is also known as bedding, which is the layering that happens in sedimentary and igneous rocks formed at the surface of the Earth that comes from lava flows or other volcanic activity. It is expressed by rock layers (units) of a general tabular or lenticular form that differ in rock type

3. Law of Unconformomities Law of Cross Cutting Relationship Law of Inclusions Law of Original Horizontality Law of Faunal Succession Law of Superposition LAWS OF STRATIGRAPHY

4. Law of Superposition The largest and heaviest rock layer that settled first at the bottom is the oldest rock layer The lightest and smallest that settled last is the youngest rock layer. Sandstone & Shale Shale & Siltstone Sandstone Limestone & Sandstone Limestone

5. Principle of Original H orizontality sediments are deposited in flat layers, if the rock maintains in horizontal layers , it means it is not yet disturbed and still has its original horizontality 1 2

6. Law of Inclusions A rock mass that contains pieces of rocks called inclusions are younger than the other rock masses. Stated that if a rock body (Rock B) contained fragments of another rock body (Rock A), it must be younger than the fragments of rock it contained. The intruding rock (Rock A) must have been there first to provide the fragments.

7. Law of Cross Cutting Relationship Stated that if a fault or other body of rock cuts through another body of rock then it must be younger in age than the rock through which it cuts and displaces . When magma intrudes to the rock, that fault or magma is younger than the rock dike  or dyke, in geological usage, is a sheet of rock that is formed in a fracture of a pre-existing rock body

8. Law of Faunal Succession Different strata contain particular assemblage of fossils by which rocks may be identified and correlated over long distances

9. Law of Unconformities R ock layers that are formed without interruptions are conformable. D escribes a layer of rock that have been deformed or eroded before another layer is deposited , resulting in rock layer mismatching An unconformity represents a long period during which deposition stopped, erosion removed previously formed rocks, and then deposition resumed Three types of unconformities: Disconformity, Angular Uncorformity and Non-conformity

10. Three Types of Unconformities Disconformity Originates from horizontal sedimentary rock layers that is lifted and the top layer eroded. New sediments are deposited when they are submerged beneath a freshwater or saltwater Angular Unconformity It originates from horizontally parallel strata of sedimentary rock that are deposited on tilted and eroded layers . It produced an angular discordance with underlying horizontal layers. Non-conformity It originates between sedimentary rocks , metamorphic or igneous rock when sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock .

11. EXAMPLES: Arrange the rock layers from OLDEST to YOUNGEST

12. EXAMPLES: Arrange the rock layers from OLDEST to YOUNGEST C, E, D, A B

13. EXAMPLES: Arrange the rock layers from OLDEST to YOUNGEST E, B, C, D, A

14. EXAMPLES: Arrange the rock layers from OLDEST to YOUNGEST A,C, B

15. EXAMPLES: Arrange the rock layers from OLDEST to YOUNGEST G , C, A, F, B, H, D, I, E

16. LESSON 2: Correlation of Rock Layers - The process of showing that rocks or geologic events occurring at different locations are of the same age Two types of correlation: Physical F ossil - Geologists need to correlate rocks from one place to another to get more complete record of Earth’s history over time . - They try to determine the relative age of widely separated strata or rock layers . - They used correlation trying to fit together sedimentary strata in different places just like a cut out puzzle.

17. 1. Physical Correlation Is accomplished by using number of criteria such as color, texture, and types of minerals contained within a stratum which make it possible for geologists to classify a particular stratum specifically 2 . Fossil Correlation Is a principle that geologists use to determine the age of rock. It uses fossil with unique characteristics, such as geologically short lifespan and easily identifiable features and use this information to estimate the age of rock layer in other areas that contain the same type of fossil or group of fossils

18. Criteria to be considered in identifying index fossils includes: Easily recognizable and it must be easy to identify because of its uniqueness. Must be geographically widespread Must lived for only a short time There are fossils which are used to date the layers of rock that they are found in. Fossils that can be used in this way are called index fossils , and rock layers with the same index fossils in them can be correlated.

19. Match correlated rock layers

20. Answer:

21. Match correlated rock layers There are four columns from neighboring regions. The numbers represent different fossils found in the rock layers. Unconformities (buried erosional surfaces) indicate that material is missing. Try to find a fossil number that is common to all four columns and use it to line them up for correlation in the previous example.

22. Answer: