Answer:
The age of the rock = 2800.6 million years = 2.8 billion years.
A simple method of analysis similar to Carbon dating is used to obtain the required age of the rock. Radioactive substances decay according to first order reaction kinetics. So, plugging all the required parameters into the general equation for amount of substance left in a first order decay gives us the age of the rock.
Explanation:
Half life of Uranium-235 = 700 million years (from literature)
The decay of radioactive substances follow first order reaction kinetics.
The general equation is given as
A(t) = A₀ e⁻ᵏᵗ
A(t) = Amount of radioactive substance left after a particular time = 6.25%
A₀ = initial amount of radioactive substance = 100%
t = time that has passed since the beginning = age of the rock = ?
k = decay constant
The decay constant is related to the half life (T) through the relation,
k = (In 2)/T
k = (0.693/700) = 0.00099 /million years
A(t) = A₀ e⁻ᵏᵗ
6.25 = 100 e⁻ᵏᵗ
0.0625 = e⁻ᵏᵗ
In e⁻ᵏᵗ = In 0.0625 = -2.7726
-kt = - 2.7726
t = (2.7726/0.00099) = 2800.6 million years
t = 2.8 billion years.
Hope this Helps!!!
Answer:
A lack of water in stores such as rivers, lakes, reservoirs and aquifers (water stored underground naturally)
i. Using fossil evidences
ii. Similar rock lithologies at the edges of continent
iii. Climate clues
iv. Fitting of the continents into a puzzle
v. Sea floor spreading
Explanation:
Pangea was a super-continent on the earth which formed about 330 million years ago during the Paleozoic and began breaking up during the early Mesozoic, about 175 million years ago.
Most of the present day continents formed as a result of the separation of the Pangea in the early Mesozoic.
The first scientist to propose the existence of this super-continent was Alfred Wegener in 1912. He suggested the continental drift hypothesis to explain the separation of the land masses.
Today, the theory has been revised to the theory of plate tectonics which provides a better mechanism to understand the drifting of the continents.
Here are some of the evidences to support the existence of Pangea;
- Using fossil evidences: Mesosaurus, a reptile animal that lived during the Permian, was found in both South America and Southern Africa. Since this animal could not swim nor fly, only a jointed landmass could have made them present in both continents.
- Similar rock lithologies at the edges of continents: rock formations at the Western edge of Africa and South - Eastern part of Brazil matches with one another and have been believed to be once joined together.
- Climatic clues such as glacial tills that are confined to temperate and polar regions have been found in tropical regions.
- Wegener fitted the present day continent into a giant supercontinent and this provided a visual support for his claim.
- Evidences from sea floor spreading revealing magnetic reversals at divergent margins suggests the prevalence of plate tectonics i.e moving plates on earth.
This among many other evidences underscores the existence of a supercontinent called Pangea.
