The lithosphere and its materials
A piece of granite, a sandy beach and an earthquake have something in common: they all happen in the lithosphere, the rigid part of the geosphere where rocks form, break and change.
What the lithosphere is
When you go down a deep mine, the temperature rises by about $3\text{ }^\circ\text{C}$ every 100 metres, which shows that the Earth's interior is very hot and that deep rocks can slowly deform: so down to what depth does a cold, completely rigid surface layer, the one we live on, remain?
Define what the lithosphere is in your own words and explain how it differs from the geosphere.
Define what the lithosphere is in your own words and explain how it differs from the geosphere.
Look at the schematic cross-section of the geosphere: the blue band marked with "?" highlights one of its regions. State which region it is and which layers form it,…
Look at the schematic cross-section of the geosphere: the blue band marked with "?" highlights one of its regions. State which region it is and which layers form it, explain the relationship between the geosphere, lithosphere, crust, and mantle, and explain why we say that this region is "rigid".
Explain the difference between the crust and the lithosphere: which of the two is thicker, which part of the mantle the lithosphere includes, and why we say the…
Explain the difference between the crust and the lithosphere: which of the two is thicker, which part of the mantle the lithosphere includes, and why we say the lithosphere is the "rigid" layer.
Rocks and minerals: the materials of the lithosphere
If you look closely at a granite kitchen worktop, you will see flecks of different colours clearly separated from one another, whereas a grain of rock salt is uniform and transparent throughout: so why do the solid materials of the Earth's surface sometimes appear as pure substances and sometimes as visible mixtures?
Explain the difference between a rock and a mineral using the example of granite, which is made of quartz, feldspar, and mica.
Explain the difference between a rock and a mineral using the example of granite, which is made of quartz, feldspar, and mica.
Classify these materials as a rock or a mineral, justifying each answer: rock salt, granite, quartz, and marble.
Classify these materials as a rock or a mineral, justifying each answer: rock salt, granite, quartz, and marble.
What are the two basic types of materials of the lithosphere studied by geology? Explain how they are related to each other.
What are the two basic types of materials of the lithosphere studied by geology? Explain how they are related to each other.
Recognising rocks and minerals around you
Classify these materials as a mineral or a rock, justifying each answer: slate, calcite, basalt, and common salt.
Classify these materials as a mineral or a rock, justifying each answer: slate, calcite, basalt, and common salt.
Is a brick a rock? Is coal a rock? Explain both answers by looking at how each material is formed: whether it is natural or manufactured, and whether it is an aggregate…
Is a brick a rock? Is coal a rock? Explain both answers by looking at how each material is formed: whether it is natural or manufactured, and whether it is an aggregate of minerals.
"A rock is like a sponge cake and minerals are its ingredients": explain what this analogy gets right and point out one important difference between baking a cake and…
"A rock is like a sponge cake and minerals are its ingredients": explain what this analogy gets right and point out one important difference between baking a cake and forming a rock.
A lithosphere that recycles itself
At the headwaters of a mountain river, a granite massif outcrops (a rock composed approximately of 30% quartz, 50% feldspar, and 20% mica). However, when analyzing the…
At the headwaters of a mountain river, a granite massif outcrops (a rock composed approximately of 30% quartz, 50% feldspar, and 20% mica). However, when analyzing the fine sand of a beach located at the mouth of that river after traveling 350 km, it is found that 95% of the grains are exclusively quartz.
- a) Interpret this change in composition and deduce what has happened to the feldspar and mica during transport compared to the resistance of quartz.
- b) A bather fills a jar with that sand and says they are "taking a rock home as a souvenir." Reason whether the loose sand should be classified as a rock, as a collection of loose minerals, or as sediment, and explain what geological process would be missing for it to become a sedimentary rock.
To investigate how earthquakes originate in a lithosphere that is solid and rigid, you carry out the following experiment in the classroom: you rest a flat, rigid…
To investigate how earthquakes originate in a lithosphere that is solid and rigid, you carry out the following experiment in the classroom: you rest a flat, rigid plastic ruler on the edge of a table, leaving half of it in the air. You push the free end downward with one finger little by little: the ruler bends slightly, resisting the force, until it suddenly snaps with a violent crack and you feel an instantaneous tremor on the table and in your hand.
- a) Interpret the model: deduce what the continuous force of your finger, the elastic bending of the ruler, the snap of the break, and the tremor vibrating through the table represent in Earth's dynamics.
- b) Based on this model, justify why the rigidity of rocks does not prevent earthquakes, but is precisely the essential condition for energy to accumulate and be released seismically instead of deforming smoothly and continuously.