ELS-Q1-M11-Formation of Rock Layers.pptx

Key Features of Rock Layers
Formation
Rock layers form through processes such as sedimentation, volcanism, and metamorphism.

Sedimentary layers: Form when particles settle in water or air and compact over time (e.g., sandstone, limestone).
Volcanic layers: Form when lava cools on the surface (e.g., basalt).
Metamorphic layers: Develop when pre-existing rocks change due to heat and pressure.
Principles of Stratigraphy

Law of Superposition: In undisturbed layers, the oldest rocks are at the bottom, and the youngest are at the top.
Principle of Original Horizontality: Sedimentary layers are originally deposited in horizontal layers.
Principle of Cross-Cutting Relationships: A feature (like a fault or intrusion) that cuts through layers is younger than the layers it disrupts.
Fossil Record

Fossils in rock layers help geologists determine the relative ages of rocks and understand past environments.
Index fossils: Found only in specific time frames, these help identify the age of the strata in which they appear.
Unconformities

Gaps in the geological record caused by erosion or non-deposition.
Types: Disconformity, Angular Unconformity, and Nonconformity.
Types of Rock Layers
Sedimentary Rocks: Formed from deposition and compaction of particles (e.g., shale, sandstone).
Igneous Rocks: Solidified from molten magma or lava (e.g., granite, basalt).
Metamorphic Rocks: Formed from existing rocks under heat and pressure (e.g., marble, schist).

1. Rock Layer Formation 1. describe how layers of stratified rocks are formed; 2. describe the different laws of stratigraphy; 3. determine how geologists correlate rock layers;

2. How are rock layers formed? Stratified rocks, also known as derivatives rock, maybe fragmental or crystalline. These rocks are products of sedimentary processes. These are made of visible layers of sediments. The formation on rock layers depend on its stratigraphy and stratification.

3. Stratigraphy - It is the branch of geology that deals with the description, correlation, and interpretation of stratified sediments and stratified rocks on and within the Earth. -It is the study of the rock layers(strata). It will give you clues to the location of ancient seas, mountains, plateaus and plains.

4. 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.

5. T wo primary methods ➢ used by geologists to determine the age of rocks, fossils, and other materials . Relative Dating Absolute Dating

6. Relative Dating Relative dating determines the order of events or the relative age of rocks by comparing them to other rocks and features. It does not provide a specific numerical age.

7. Relative Dating Output : The result is a sequence or order of events (e.g., "Rock layer A is older than rock layer B "). Usage: Commonly used in sedimentary rock formations and in stratigraphy, helping to create a relative timeline of geological events and formations.

8. Stratigraphic Laws Stratigraphic laws are basic principles that all geologists use in decoding or deciphering the spatial and temporal relationships of rock layers.

9. 1. Law of Superposition ➢ In any undisturbed sequence of sedimentary rock layers, the oldest layer is at the bottom, and the youngest layer is at the top .

10. 2. Law of Original Horizontality ➢ Layers of sediment are originally deposited horizontally under the action of gravity.

11. 3. Law of Lateral Continuity ➢ Layers of sediment initially extend laterally in all directions until they thin out or encounter a physical barrier.

12. 4. Law of Cross Cutting Relationship ➢ a fault or dike- a slab rock cuts through another rock Any geological feature (e.g., fault, intrusion) that cuts across a rock layer must be younger than the layer it cuts through.

13. 5. Law of Inclusions ➢ A rock mass that contains pieces of rocks called inclusions are younger than the other rock masses .

14. 6 . Law of Unconformities ➢ rock layers that are formed without interruptions are conformable. ➢ describes a layer of rock that have been deformed or eroded before another layer is deposited, resulting in rock layer mismatching

15. 7 . Law of Faunal Succession ➢ first recognized by William Smith ➢ different strata contain particular assemblage of fossils by which rocks may be identified and correlated over long distances

16. Absolute Dating Absolute dating, also known as numerical dating, provides a specific age or date for a rock or fossil, expressed in years .

17. Absolute Dating Output: The result is a numerical age (e.g., "This rock is 50 million years old ").

18. Absolute Dating Usage: Commonly used for dating igneous rocks and volcanic layers, as well as for archaeological artifacts and fossils that contain organic materials.

19. Radiometric Dating Radiometric dating is a technique used to date materials such as rocks, fossils, and archaeological artifacts by measuring the decay of radioactive isotopes within them.

20. Types of Radiometric Dating Carbon-14 Dating (Radiocarbon Dating ) Material dated: Organic materials, such as wood, bone, shells, and other biological materials . Time range: Up to about 50,000 years.

21. Types of Radiometric Dating 2. Potassium-Argon (K- Ar ) Dating Material dated: Volcanic rocks and minerals, particularly those containing potassium . Time range: From about 100,000 years to billions of years.

22. Types of Radiometric Dating 3. Uranium-Lead (U- Pb ) Dating Material dated: Zircon crystals, and other uranium-rich minerals . Time range: From about 1 million years to over 4.5 billion years.

23. Types of Radiometric Dating 4. Rubidium-Strontium ( Rb-Sr ) Dating Material dated: Igneous and metamorphic rocks, and minerals such as mica, feldspar, and Time range: From about 10 million years to over 4 billion years.

24. Types of Radiometric Dating 5. Uranium-Thorium Dating Material dated: Carbonates, such as coral and cave formations (speleothems), and marine sediments . Time range: From a few thousand years to about 500,000 years.

25. Types of Radiometric Dating 6. Lead-Lead ( Pb-Pb ) Dating Material dated: Oldest rocks, meteorites . Time range: Up to 4.5 billion years.