The document outlines several basic principles and laws of geology, including: 1. Neptunism and plutonism, which are opposing theories on the formation of rocks. 2. Uniformitarianism, the principle that geological processes have remained consistent over time. 3. Laws established by Nicolaus Steno on the ordering and orientation of rock layers. 4. Additional principles on cross-cutting relationships, inclusions, and faunal succession.

1. Basic Principals/Laws of Geology
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

2. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

3. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

4. Basic Principals of Geology:
1. Neptunism: Abraham Gottlob Werner (1749-1817)
2. Plutonism: James Hutton (1726-1797)
3. Catastrophism: James Ussher (1581-1656)
4. Uniformitarianism: James Hutton (1726-1797)
5. Law of Superposition: Nicolaus Steno (1638-1687)
6. Law of Original Lateral Continuity: Nicolaus Steno (1638-1687)
7. Law of Original Horizontality: Nicolaus Steno (1638-1687)
8. Law of Cross-cutting Relationships: Charles Lyell (1797-1875)
9. Principle of Inclusions: Charles Lyell (1797-1875)
10. Principle of Faunal Succession: William Smith (1769-1839)
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

5. William Smith
Father of Historical Geology
Charls Lyell
Werner
James Hutton
Father of modern Geology
Nicolaus Steno
Father of Geology
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)
James Usher

6. Principles of Historical Geology
Neptunism vs. Plutonism
Neptunism: Abraham Gottlob Werner (1749-1817): The theory states that the rocks of the Earth's crust
consists of materials deposited from, or crystallized out of the ocean.
Plutonism: James Hutton (1726-1797): The concept of the formation of crystalline rocks by
solidification from a melt or magma.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

7. Uniformitarianism: James Hutton (1726-1797): The fundamental principle that geological processes
and natural laws now operating to modify the Earth's crust have acted in much the same manner
(gradual) and with essentially the same intensity throughout geologic time, and that past geologic events
can be explained by forces observable today. "The present is the key to the past"
Principles of Historical Geology
Catastrophism vs. Uniformitarianism
Catastrophism: James Ussher (1581-1656): The doctrine that sudden violent, short-lived, more or
less worldwide events outside our present experience or knowledge have greatly modified the Earth's
crust accounting for its present configuration as well as for the observed distribution of life forms.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

8. Catastrophism Uniformitarianism
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

9. Law of Superposition
Nicolaus Steno (1638-1687)
▪ In a series of undeformed sedimentary rocks: Oldest rocks are at the bottom (D) - deposited first;
Youngest rocks are on the top (A) - deposited last.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

10. Law of Original Lateral Continuity
Nicolaus Steno (1638-1687)
• When they form, horizontal strata
continue in all directions until they:
• Thin to nothing,
• Change into something else,
• Abut against a barrier.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

11. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

12. Law of Original Horizontality
Nicolaus Steno (1638-1687)
• Sedimentary rocks are formed in layers (strata) which were originally horizontal.
• Flat strata are probably undisturbed
• Tilted strata have been affected by tectonics.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

13. Principle of Cross-cutting Relationships
Charles Lyell (1797-1875)
• Crosscutting igneous rocks are younger than what they intrude.
• Faults are younger than what they cut.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

14. • Erosion surfaces exist in the rock record.
• Fragments within strata above are derived from the older strata below → they are older than the strata
containing them.
• The strata containing the fragments are younger than the strata the fragments came from.
Principle of Inclusions
Charles Lyell (1797-1875)
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

15. ▪ Fossil organisms succeed one another in a definite,
determinable order.
Principle of Faunal Succession
William Smith (1769-1839)
• Plants and animals evolve through time and specific
fossils are often diagnostic of geologic periods.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

16. Principle of Faunal Succession
William Smith (1769-1839)
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

17. Geologic Time
Time – a manmade concept; based on recurrent natural
phenomenon
Why is time important? - To place events into context, i.e.
when and for how long did an event take place
Geologic Time – Geological events arranged in relation to
time
Relative Dating - The age of a rock, fossil, or other feature
measured relative to another.
Absolute Dating (numerical dating) - The age of a rock in
years.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

18. Basis of Relative Dating
• Superposition
• Lateral Continuity
• Original Horizontality
• Inclusions
• Cross-cutting Relationships
• Fossil Records:
• Based on evolution
• Also relics of superposition
• When a species becomes extinct, it does not reappear.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

19. • Radioactive decay - spontaneous transformation of an element to another isotope of the
same element or another element.
Alpha Decay – loss of a positively charged He ion
Beta Decay – neutron splits into zproton and electron
• Isotope - element with different number of neutrons in the nucleus.
• Half life - The fixed period of time during which half the parent atoms present in a closed
system decay to form daughter atoms.
Radioactive Dating
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

20. Radioactive isotope Stable isotope of other element
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

21. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

22. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)