A measure of the amount of light given off by a star is its absolute luminosity or magnitude. Absolute magnitude<span> is the measure of </span>intrinsic brightness<span> of a celestial object. It is the hypothetical </span>apparent magnitude<span> of an object at a standard </span>distance<span> of exactly 10 </span>parsecs<span> (32.6 </span>light years<span>) from the </span>observer<span>, assuming no </span>astronomical extinction<span> of starlight. </span>
Answer:
Divergent boundaries such as the mid-oceanic ridge system.
Explanation:
Divergent boundaries occur when plate boundaries pull away from each other. Molten rock or magma rise from the gap between the two plates, rising up to the sea floor where it cools down to form new crust. It is the mid-ocean ridges where you see the most magma produced and there has not been any other tectonic event or area that could match its procution since the Precambrian period.
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.
The troposphere because it has half of all air in the Atmosphere
