Precambrian Era rocks are some of the oldest on the earth. they can be found in ancient regions of the continents called cratons. A craton can be found in South Africa but the oldest rocks to date can be found in Australia. Precambrian Era rocks require a radiometric dating method that is accurate for such a long time. An appropriate method to use is uranium lead radiometric dating. The Precambrian Era on earth was a hostile one. it's important to study it because many planets could have or could have had the same conditions and it is a step to finding out how life evolved on earth.
Answer:
1384.83 miles .
Explanation:
1 .
Conversion of kilometer to mile ,
1 kilometer is equal to 0.621 mile ,
The lower mantle is 2230 km can be converted to miles , by simply multiplying by the value 0.621 .
Hence ,
the conversion is done as follows ,
2 .
Lower mantle = 2230 km = 2230 * 0.621 = 1384.83 miles
hence , the value of lower mantle is 2230 km and in terms of mile is equal to 1384.83 miles .
What imaginary line cuts across the top of south america?
The Equator
Answer:
A) sea level drops; land subsides
Explanation:
The sea is the final destination of all streams on land. All streams empty into seas which are the basins that collects all terrestrial materials.
The base level is the lowest level to which a river can erode its channel. The base level is greatly influenced by what happens to a sea.
When a river reaches its base level, erosion ceases. If a river is young and set above its base level, we see a rapid rate of erosion.
A sea, the final basin of depostion of rivers controls the base level to a very large extent. When there is a tectonic movement and a sea subsides. It becomes more deeper and lower. Sea level also falls and materials grades seaward. A river would cut rapidly along its channel and its bed to measure up to the level of the ocean.
Therefore, we see a very rapid rate of erosion of channels when sea level falls and the earth sags downward. This would lead to a lower base level.
When sea level rises and there is a tectonic uplift, rivers erode their channels less and begins to aggrade materials. The base level also rises.
Answer:The eastern Terai is cooler than the western one because it is closer to the sea (Bay of Bengal).
