Artificial Sources to Study Earth’s Interior
Artificial sources are those sources which are derived from mathematical assumptions and calculations. Important among them are:
- Density
- Pressure
- Temperature
Density
The earth is made up of various types of rocks. Rocks are composed of minerals. Rock may be composed of one mineral or many minerals. The characteristics and properties of the minerals determine the rocks.
The rocks under our feet while walking can be examined well in our laboratory. The rocks of various places are not alike but are different. The rocks lying in our agricultural field are other than the mined rocks. It could be different types like igneous or sedimentary, or metamorphic.
The rocks of the earth’s surface are different from the interior. Studying the density is one way to know it. The density is the property of the rock’s compactness. When the molecules of the rocks are very close, it is denser. In other words, it is defined as the relationship between the mass of the rock and how much volume it occupies. Thus, a rock with greater mass and lesser volume will become denser, but the density is lower when the mass is less and the volume is more. Therefore, density is equal to the mass of the rock divided by its volume.
D = m / v
Where
D = Density,
m = mass of the rock and
v = volume of the same rock
This formula expresses the result received as that much gram/cm3.
For the first time, British scientist Henry Cavendish (1798) probably attempted to calculate the earth’s density based on Newton’s law of Gravitation. He found it to be 5.48 gm/cm3. Poynting (1878) calculated the earth’s density and found it to be 5.49 gm/cm3.
The density of the rocks found at the surface rocks: 2.7 – 2.9 gm/cm3
The density of rocks found at the sea floor is around: 3.0 gm/cm3
It is quite obvious that the central part of the earth is more than: 5.5 gm/cm3
The average density of the earth: 5.52 gm/cm3
The density calculated at different depths in the earth’s interior is given in the following Table.
Depth in km | Density in gram/cm3 |
(Surface/ Sea Level) 0 | 2.70 to 2.90 |
100 | 3.38 |
Ite 500 | 3.85 |
1000 | 4.58 |
2000 | 5.12 |
2890 | 5.56 |
2900 | 9.90 |
4000 | 11.32 |
5000 | 12.12 |
5500 | 12.92 |
6371 | 13.09 |
It is also very clear through the Table that the density of the innermost part of the earth is around 13 gm/cm3. The increase in the density in the earth’s interior is not a continuous affair but changes very abruptly at different depths. The changing density at different depths in the interior may very clearly be seen at a glance in Fig.
Pressure
It is obvious that the density of the rocks in the interior is greater. It is scientifically proven that the density of matter is increased when it is compressed. Earlier, it was assumed that the density of the interior rock is greater due to the increasing pressure of the rocks lying above. To some extent, this assumption is true, but it is also a universally proven fact that the density of the rocks cannot be increased beyond a certain limit simply by compression or more pressure.
Hence, the inference that the increasing pressure is the reason for greater density is not true. The higher dense material of the interior can be explained through the constituent of the rocks. It is now confirmed that the core is composed of essentially heavy metallic materials which have higher density. The pressure in the interior keeps on increasing with depth (Fig).
Temperature
With the advancement in technology and know-how to use the minerals, mining activities started. We have been digging the earth for many centuries. But the deeper mining and oil exploration has led to drilling the crust to a much deeper level in recent times.
Our observations record a rate of increase in temperature, and it is about 3°C per 100-meter depth or about 30°C per km. If we calculate the temperature at this rate, the earth’s core would witness a temperature of more than 1,90,0000 C. it is unimaginable. Probably, this much of high temperature would melt the entire earth.
The above calculation has not taken the increasing pressure into account. A recent experiment conducted and calculated by scientists suggests that the inner part of the earth, the core, has about 50000 C temperature with a variation of 5000 C plus or minus. Hence, these two temperatures are contradictory to each other.
The temperature increase observed in the earth’s top layer is not constant. The rate may be higher near the surface for a few km, but it is not true for the much deeper part of the earth.
The above conditions could very well be explained by the presence of radioactive minerals in the top layers of the crust. Granitic rocks are very well known for the abundance of radioactive minerals like uranium and thorium. The higher temperature in the granitic layer was found accounted due to chemical disintegration. The process of fission and fusion of these minerals generates a huge amount of heat. This leads to greater temperature in this zone of the earth’s strata.
With increasing depth, the availability of radioactive minerals is less and hence, lesser temperature. Therefore, there is a decrease in the rate of temperature with depth. The observed temperature and temperature needed to melt the rock at different depths are shown by a graphical representation in Fig.
Relationships of Density, Pressure and Temperature with Depths
We have already deliberated above about the density, pressure and temperature in the earth’s interior. From these discussions, it is clear that all three components are increasing with increasing depth. Their increase is not uniform continuously but with changing rates. The reasons for their increase are already explained while dealing with those components. Their relationships are very clearly seen in Fig.
Read More in Geomorphology
- Earth Movements: Meaning and Types
- Epeirogenic Earth Movements
- Orogenic Earth Movements
- Cymatogenic Earth Movements
- Concept of Stress and Strain in Rocks
- Folds in Geography
- Fault in Geography
- Mountain Building Process
- Morphogenetic Regions
- Isostasy: Concept of Airy, Pratt, Hayford & Bowie and Jolly
- Continental Drift Theory of Alfred Lothar Wegener (1912)
- Plate Tectonics: Assumptions, Evidences, Plate Boundaries and Features Formed
- Volcanoes: Process, Products, Types, Landforms and Distribution
- Earthquakes: Processes, Causes and Measurement
- Plate Tectonics and Earthquakes
- Composition and Structure of Earth’s Interior
- Artificial Sources to Study Earth’s Interior
- Natural Sources to Study Earth’s Interior
- Internal Structure of Earth
- Chemical Composition and Layering of Earth
- Weathering: Definition and Types
- Mass Wasting: Concept, Factors and Types
- Models of Slope Development: Davis, Penck, King, Wood and Strahler
- Davis Model of Cycle of Erosion
- Penck’s Model of Slope Development
- King’s Model of Slope Development
- Alan Wood’s Model of Slope Evolution
- Strahler’s Model of Slope Development
- Development of Slope
- Elements of Slope
- Interruptions to Normal Cycle of Erosion
- Channel Morphology and Classification
- Drainage System and Drainage Pattern
- River Capture or Stream Capture
- Stream Channel Pattern
- Fluvial Processes and Landforms: Erosional & Depositional
- Delta: Definition, Formation and Types
- Aeolian Processes and Landforms: Erosional & Depositional
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- Glacial Landforms: Erosional and Depositional
- Periglacial: Meaning, Processes and Landforms
- Karst Landforms: Erosional and Depositional
- Karst Cycle of Erosion
- Coastal Processes: Waves, Tides, Currents and Winds
- Coastal Landforms: Erosional and Depositional
- Rocks: Types, Formation and Rock Cycle
- Igneous Rocks: Meaning, Types and Formation
- Sedimentary Rocks: Meaning, Types and Formation
- Metamorphic Rocks: Types, Formation and Metamorphism
- Morphometric Analysis of River Basins
- Soil Erosion: Meaning, Types and Factors
- Urban Geomorphology: Concept and Significance
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- Geomorphic Hazard- Avalanches: Definition, Types and Factors
- Integrated Coastal Zone Management: Concept, Objectives, Principles and Issues
- Watershed: Definition, Delineation and Characteristics
- Watershed Management: Objective, Practice and Monitoring
- Applied Geomorphology: Concept and Applications