GEOLOGICAL CONCEPTS FIVE STEPS TO BECOMING A GEOLOGICAL

GEOLOGICAL CONCEPTS FIVE STEPS TO BECOMING A… GEOLOGICAL DETECTIVE!

OUR GOAL: TO INTERPRET GEOLOGICAL STRUCTURES WE SEE, LIKE THE ROADCUT DEPICTED BELOW

THE 5 CONCEPTS v UNIFORMITARIANISM v ORIGINAL HORIZONTALITY v LATERAL CONTINUITY v SUPERPOSITION v LAW OF CROSS-CUTTING RELATIONSHIPS

CONCEPT: UNIFORMITARIANISM USING HISTORY, WE STUDY THE PAST TO UNDERSTAND THE PRESENT… BUT USING UNIFORMITARIANISM, WE STUDY THE PRESENT GEOLOGICAL PROCESSES TO UNDERSTAND THE PAST GEOLOGICAL PROCESSES (EVENTS THAT HAPPENED MILLIONS OF YEARS AGO)… DEFINITION: GEOLOGICAL PROCESSES HAPPENING TODAY HAPPENED IN THE PAST… EXAMPLE: TO UNDERSTAND MOUNTAINS THAT FORMED MILLIONS OF YEARS AGO, WE STUDY HOW MOUNTAINS ARE FORMING TODAY.

APPLICATION 1 OF UNIFORMITARIANISM: WHAT ARE THE HORIZONTAL LINES?

CLUE FROM PRESENT PROCESS…

HERE IT IS AGAIN… USING TIME LAPSE PHOTOGRAPHY

ANCIENT LAKE

DRYING UP

LEAVING TERRACE LINES

APPLICATION 2 OF UNIFORMITARIANISM: WHAT IS THIS?

CLUE FROM PRESENT PROCESS… FROM ANCIENT MUD FLAT OR SAND DUNE THEY MUST HAVE SOLIDIFIED INTO ROCK

APPLICATION 3 OF UNIFORMITARIANISM: EXPLAIN THIS SOLID ROCK…

CLUE FROM PRESENT PROCESS… GRAVEL RIVERBED BEACH THEY MUST HAVE SOLIDIFIED INTO ROCK

FROM UNIFORMITARIANISM COMES THE OTHER 4 CONCEPTS v ORIGINAL HORIZONTALITY v LATERAL CONTINUITY v SUPERPOSITION v LAW OF CROSS-CUTTING RELATIONSHIPS

CONCEPT: ORIGINAL HORIZONTALITY SEDIMENT LAYERS ARE USUALLY DEPOSITED HORIZONTALLY THUS, LOOK FOR LAYERS NO LONGER HORIZONTAL TO RECOGNIZE THAT FORCES ACTED ON THE LAYERS AFTER FORMATION

APPLICATION OF ORIGINAL HORIZONTALITY: FINDING TILTED AND FOLDED LAYERS WHAT HAPPENED TO THE LAYERS HERE? BY FORCES PUSHING TOGETHER

SUMMARY OF ORIGINAL HORIZONTALITY v SEDIMENT LAYERS ARE USUALLY DEPOSITED HORIZONTALLY v SO, LOOK FOR LAYERS THAT ARE NOT HORIZONTAL, MEANING SOME FORCE ACTED ON THEM TO FOLD OR TILT THEM v USE THIS CONCEPT TO FIND FOLDS AND TILTED ROCK LAYERS

CONCEPT: LATERAL CONTINUITY ROCK LAYERS CAN BE TRACED ACROSS WIDE AREAS

APPLICATION OF LATERAL CONTINUITY: WHAT HAPPENED TO THE LAYERS HERE? BROKEN THEY WERE

APPLICATION OF LATERAL CONTINUITY: FINDING FAULTS FORCES ACTED ON THE ROCK LAYERS TO BREAK THEM! CREATING A FAULT (BROKEN ROCK LAYERS). BROKEN THEY WERE

2 ND APPLICATION OF LATERAL CONTINUITY: WHAT HAPPENED TO THE LAYER BETWEEN THESE TWO ARROWS?

2 ND APPLICATION OF LATERAL CONTINUITY: FINDING EROSION REMOVED THE MATERIAL AS THE RIVER CUT DOWNWARD

2 ND APPLICATION OF LATERAL CONTINUITY: FINDING EROSION REMOVED PART OF THE LATERALLY CONTINUOUS LAYERS AFTER THE LAYERS WERE FOLDED UPWARD WHAT HAPPENED HERE?

SUMMARY OF LATERAL CONTINUITY v ROCK LAYERS ARE DEPOSITED (SO CAN BE TRACED) ACROSS WIDE AREAS v SO, LOOK FOR BREAKS IN THE CONTINUITY v AND USE THIS CONCEPT TO FIND FAULTS AND AREAS THAT HAVE EXPERIENCED EROSION

CONCEPT: SUPERPOSITION YOUNGER ROCK LAYERS YOUNGER USUALLY OVERLIE OLDER ROCK LAYERS AS NEW SEDIMENT DEPOSITS ON TOP OF EXISTING SEDIMENT

APPLICATION OF SUPERPOSITION: WHICH ROCK LAYER IS YOUNGER? A? OR B?

APPLICATION OF SUPERPOSITION: DETERMINING RELATIVE AGES OF LAYERS ROCK LAYER A IS YOUNGER A NOT <<<<< YOUNGER OLDER >>>>> B

2 ND APPLICATION OF SUPERPOSITION: WHICH ROCK LAYER IS YOUNGER? OR A? B?

2 ND APPLICATION OF SUPERPOSITION: DETERMINING RELATIVE AGES OF LAYERS ROCK LAYER A IS YOUNGER OR A? B?

SUMMARY OF SUPERPOSITION v YOUNGER ROCK LAYERS USUALLY OVERLIE OLDER ROCK LAYERS v SO, LOOK FOR ROCK LAYERS ONE ON TOP OF THE OTHER v USE THIS CONCEPT TO FOLLOW THE HISTORICAL SEQUENCE OF EVENTS HAPPENING AT A GIVEN SPOT

CONCEPT: LAW OF CROSS-CUTTING RELATIONSHIPS MAGMA INTRUSION: CALLED A DIKE MOLTEN ROCK: CALLED MAGMA INTRUDING ROCK IS YOUNGER THAN THE ROCK INTO WHICH IT INTRUDES

APPLICATION OF CROSS-CUTTING RELATIONSHIPS: WHICH ROCK IS YOUNGER? A? OR B?

APPLICATION OF CROSS-CUTTING RELATIONSHIPS: DETERMINING RELATIVE AGE OF ROCKS “B” IS YOUNGER BECAUSE “B” INTRUDED THROUGH LAYER A INTRUSION A? OR B?

SUMMARY OF CROSS-CUTTING RELATIONSHIPS v INTRUDING ROCK IS YOUNGER THAN THE ROCK INTO WHICH IT INTRUDES v SO LOOK FOR INTRUSIONS, ROCK THAT IS DIFFERENT FROM AND CUTS THROUGH OTHER TYPES OF ROCK v USE THIS CONCEPT WITH SUPERPOSITION TO FOLLOW THE HISTORICAL SEQUENCE OF EVENTS HAPPENING AT A GIVEN SPOT

REVIEW 1 1 2 3 1. HOW CAN YOU APPLY ORIGINAL HORIZONTALITY? A. LOOK FOR LAYERS NOT HORIZONTAL TO FIND FOLDS AND TILTED ROCK 2. HOW CAN YOU APPLY LATERAL CONTINUITY? A. LOOK FOR BREAK IN CONTINUITY TO FIND FAULTS AND EROSION 3. HOW CAN YOU APPLY SUPERPOSITION? A. TO DETERMINE THE HISTORICAL SEQUENCE OF EVENTS HERE

REVIEW 2 WHICH IS YOUNGER… 1. LAYER 1 OR 2? A. LAYER 2 SUPERPOSITION 2. LAYER 2 OR DIKE B? A. DIKE B CROSS-CUTTING REL. LAYER 2 LAYER 1 3. VOLCANO A OR B? A. VOLCANO A 4. FAULT A OR B? A. FAULT A