The deepest hole ever drilled, the Kola Superdeep Borehole, barely reached 12 km in depth before the temperature and pressure made it unworkable. Compared with the $6{,}371\ \text{km}$ that separate the surface from the center of the Earth, that is an insignificant mark. Our entire picture of the planet's interior therefore comes from indirect methods.
Methods for studying the Earth's interior
The deepest mines barely reach $4\ \text{km}$ and boreholes $12\ \text{km}$, yet we know for certain that at a depth of $2{,}900\ \text{km}$ there is a layer of liquid metal: how can we map the interior of a planet if we have only scratched its crust?
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The deepest mine in the world reaches a depth of barely $4\ \text{km}$, while the radius of the Earth is about $6\,370\ \text{km}$. Explain why almost everything we know…
The deepest mine in the world reaches a depth of barely $4\ \text{km}$, while the radius of the Earth is about $6\,370\ \text{km}$. Explain why almost everything we know about the Earth's interior comes from indirect methods, and give one example of a direct method and one of an indirect method.
S-type seismic waves do not pass through the outer core, whereas P-waves do, although their speed is reduced. What does this fact tell us about the physical state of the…
S-type seismic waves do not pass through the outer core, whereas P-waves do, although their speed is reduced. What does this fact tell us about the physical state of the outer core? Explain your reasoning.
The Earth is like a peach with a thin skin, a thick juicy layer, and a pit in the center. Scientists group the layers by what they are made of.
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Order the following layers of the geosphere from the surface to the center of the planet: inner core, mantle, outer core, crust. Then state which of them occupies the…
Order the following layers of the geosphere from the surface to the center of the planet: inner core, mantle, outer core, crust. Then state which of them occupies the largest part of the Earth's volume.
At the surface, rocks break suddenly during earthquakes along faults like the San Andreas Fault, yet in mountain ranges we see strata of solid rock folded in gentle curves as if they were made of plasticine: why do the same materials behave so differently at different depths?
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Explain in your own words what the lithosphere is, which layers of the geosphere form it, and how it differs from the crust.
Explain in your own words what the lithosphere is, which layers of the geosphere form it, and how it differs from the crust.
In the gold mines of South Africa, almost 4 km underground, the rock walls are at over $50\ ^{\circ}\text{C}$ (about $122\ ^{\circ}\text{F}$) and the air has to be cooled with tons of ice: at what rate does the interior of the geosphere heat up, and what effect does that heat have on the deep rocks?
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Look at the diagram of the Earth's interior. Name the layers marked with numbers 1 to 4 and state one characteristic of each (physical state or composition).
Look at the diagram of the Earth's interior. Name the layers marked with numbers 1 to 4 and state one characteristic of each (physical state or composition).
Convection currents exist in the mantle: hot material rises and cold material sinks. Explain what causes these currents and how they relate to the movement of the…
Convection currents exist in the mantle: hot material rises and cold material sinks. Explain what causes these currents and how they relate to the movement of the lithosphere.
Back to the beginning: At a depth of 12 km in the Kola borehole, the temperature reached about $180\ ^{\circ}\text{C}$ (about $356\ ^{\circ}\text{F}$); the average gradient there was lower than the typical $30\ ^{\circ}\text{C/km}$. The rock, hot and under enormous pressure, behaved plastically and tended to close the hole, making it impossible to keep drilling. That is why scientists rely on indirect methods.
Summary
Let's practice! 3 medium exercises in this section