How Layers of Rocks (Stratified Rocks) are Formed? TABLE OF CONTENTS STENO’S LAWS OF STRATIGRAPHY STRATIFICATION AND ITS PROCESSES 1. 2. 3. 4. 5. Weathering and Erosion Transportation Deposition Compaction Cementation 1. Law of Superposition 2. Law of Original Horizontality 3. Law of Lateral Continuity 4. Law of Cross-Cutting Relationships QUIZ INTRODUCTION Trilobite Pterodactyl Saber Tooth Tiger STRATIFIED ROCKS Are rocks that have visible bands or layers of minerals called STRATA. These rock layers are commonly Sedimentary rocks because their formation processes are similar. Stratified rocks and Sedimentary rocks are both formed through Weathering, Erosion, Deposition, and Compaction. HOW ROCK LAYERS ARE FORMED? STRATIFIED ROCKS Examples: Sandstone Shale Marble STRATIFICATION Is the process by which sedimentary rocks are formed in distinct layers, or strata, over time. These layers are a result of the accumulation and deposition of sediments. HOW ROCK LAYERS ARE FORMED? STAGES OF STRATIFICATION 1. WEATHERING Weathering breaks down rocks into smaller particles, and erosion transports these particles away. This process exposes fresh rock surfaces for further weathering. HOW ROCK LAYERS ARE FORMED? STAGES OF STRATIFICATION 2. EROSION/TRANSPORTATION Agents like water, wind, or ice transport the weathered particles (sediments) to new locations. HOW ROCK LAYERS ARE FORMED? STAGES OF STRATIFICATION DIAGRAM HOW ROCK LAYERS ARE FORMED? Diagram pt. 1 STAGES OF STRATIFICATION 3. DEPOSITION When the transporting agents lose their energy (e.g., due to slowing water currents or wind), they deposit the sediments. The deposited sediments accumulate in layers.ns. HOW ROCK LAYERS ARE FORMED? STAGES OF STRATIFICATION 4. COMPACTION Over time, the weight of the overlying sediments causes the lower layers to become compacted. This compaction reduces the pore spaces between grains, leading to the formation of sedimentary rock. . HOW ROCK LAYERS ARE FORMED? STAGES OF STRATIFICATION 5. CEMENTATION Minerals carried by groundwater can precipitate in the pore spaces between sediments, acting as cement. This process solidifies the sediments into a cohesive rock. HOW ROCK LAYERS ARE FORMED? HOW ROCK LAYERS ARE FORMED? STENO‘S LAWS OF STRATIGRAPY The study of rock strata is called Stratigraphy. The laws of stratigraphy can help scientists understand Earth’s past. The laws of stratigraphy are usually credited to a geologist from Denmark named Nicolas Steno in the 17th century. STENO’S LAWS OF STRATIGRAPHY 1. LAW OF SUPERPOSITION Superposition refers to the position of rock layers and their relative ages. Relative age means age in comparison with other rocks, either younger or older. New rock layers are always deposited on top of existing rock layers. Therefore, deeper layers must be older than layers closer to the surface. HOW ROCK LAYERS ARE FORMED? STENO’S LAWS OF STRATIGRAPHY 2. LAW OF ORIGINAL HORIZONTALITY The law states that sediments were originally deposited horizontally by gravity. If sedimentary rock layers are tilted, they must have moved after they were deposited. This allows scientists to infer that something must have happened to the rocks to make them tilted. This includes mountainbuilding events, earthquakes, and faulting. HOW ROCK LAYERS ARE FORMED? STENO’S LAWS OF STRATIGRAPHY 3. LAW OF LATERAL CONTINUITY Law of Lateral Continuity Rock layers extend laterally, or out to the sides. Layers of rock are continuous until they encounter other solid bodies, like mountains, that block their deposition or until they are acted upon by geological processes such as erosion and fault movements. This law is used to help identify the age of rocks and identify layers of rocks that are related despite being separated. HOW ROCK LAYERS ARE FORMED? STENO’S LAWS OF STRATIGRAPHY 4. LAW OF CROSS-CUTTING RELATIONSHIPS States that any geologic feature or rock unit that cuts or deforms another is younger than the rock body or geologic structure it cuts or deforms. The cross-cutting feature is the younger feature because there must be something previously there to cross-cut. HOW ROCK LAYERS ARE FORMED? DIAGRAM whahah HOW ROCK LAYERS ARE FORMED? Summary STRATIFIED ROCKS THESE ARE ROCKS THAT HAVE VISIBLE BANDS OR LAYERS CALLED STRATA. STRATIFICATION THE PROCESS BY WHICH SEDIMENTARY ROCKS ARE FORMED IN DISTINCT STRATA OVER TIME. STRATIGRAPHY THE STUDY OF ROCK STRATA. Summary STENO'S LAWS OF STRATIGRAPHY THESE ARE CREDITED TO NICOLAS STENO, A GEOLOGIST IN THE 17TH CENTURY. LAW OF SUPERPOSITION: STATES THAT, WITHOUT ANY INTERFERENCE, THE YOUNGEST LAYER MUST BE ON TOP AND THE OLDEST LAYER ON THE BOTTOM. LAW OF ORIGINAL HORIZONTALITY STATES THAT SEDIMENTS ARE ORIGINALLY DEPOSITED HORIZONTALLY BY GRAVITY AND ANY SLOPING MUST HAVE OCCURRED AFTER THE LAYERS ARE FHORMED. Summary LAW OF LATERAL CONTINUITY WITHOUT ANY BARRIERS, STRATIFIED ROCKS ARE CONTINUOUS LATERALLY UNTIL EVENTS LIKE EROSION AND FAULTING ACT UPON THEM. LAW OF CROSS-CUTTING RELATIONSHIPS STATES THAT THE GEOLOGIC FEATURE WHICH CUTS ANOTHER IS THE YOUNGER ONE. THANK YOU! Keep Pushing, Little by Little. HOW ROCK LAYERS ARE FORMED? "You are at your strongest when you are calm." "be careful of what you ignore." QUIZ TEN MINUTES I. IDENTIFICATION 1. These Laws are credited to Nicolas Steno, a geologist in the 17th century. 2. The study of rock layers. 3. The process by which sedimentary rocks are formed in distinct Strata over time. 4. These are rocks that have visible bands or layers called Strata. 5. The visible bands or layers of minerals in rocks. 6-8. List the three Laws of Stratigraphy. 9-10. List two key processes of Stratification QUIZ 5 MINUTES II. TRUE OR FALSE (NO TWIST) 1. Stratified rocks are characterized by visible bands or layers of minerals called STRATA. 2. Steno's Laws of Stratigraphy are credited to a geologist named Nicholás Steno in the 18th century. 3. The laws of stratigraphy are used to help scientists 4. understand Earth's past by studying the relative ages and positions of rock layers. 4. The Law of Original Horizontality suggests that sediments were originally deposited vertically by gravity. 5. Cementation involves minerals carried by groundwater precipitating in pore spaces, solidifying sediments into cohesive rock. QUIZ 5 MINUTES II. TRUE OR FALSE (NO TWIST) 6. Some examples of Stratified Rocks include Sandstone, Shale, and Marble. 7. Compaction, caused by the weight of overlying sediments, reduces pore spaces between grains, forming sedimentary rock. 4. 8. The Law of Superposition states that new rock layers are always deposited below existing rock layers. 9. Layers of rock are continuous until they encounter geological processes such as erosion and fault movements. 10. Transportation involves agents like water, wind, or ice that transport weathered particles (sediments) to new locations.
