In physical geography, what does tectonic activity primarily do to the Earth's crustal rocks?

Introduction / Context:
Tectonic activity refers to the movement and interaction of large lithospheric plates that make up the outer shell of the Earth. This movement is responsible for many of the major features and processes in physical geography, including mountain building, earthquakes, rift valleys, ocean trenches, and volcanic arcs. A common examination question asks what tectonic forces actually do to the solid crustal rocks. Understanding this effect is vital for topics such as plate tectonics, structural geology, and landform development in world geography.

Given Data / Assumptions:
- The question focuses on the general effect of tectonic activity on crustal rocks.
- We consider processes such as compression, tension, and shearing that arise when plates move together, move apart, or slide past one another.
- The options list possible outcomes, including breaking, bending, or having no real effect on rocks.

Concept / Approach:
When tectonic plates interact, stress is applied to the rocks in the crust. Depending on the type and intensity of stress, rocks may fracture, fault, fold, or deform in various ways. At convergent boundaries, compression often folds and faults rocks, forming mountains. At divergent boundaries, tension can fracture and thin the crust, creating rift valleys and mid ocean ridges. At transform boundaries, shear stress can cause strike slip faults. Thus, the most accurate general statement is that tectonic activity breaks and bends crustal rocks, leading to structural deformation and reorganization of the crust.

Step-by-Step Solution:
Step 1: Recall that tectonic forces include compression, tension, and shear caused by movements of the lithospheric plates. Step 2: Under high stress, brittle rocks can crack and break, leading to faults and fractures in the crust. Step 3: Under certain conditions, especially deep in the crust where temperature and pressure are higher, rocks behave in a more plastic manner and can bend or fold rather than shatter. Step 4: These folds and faults together represent the breaking and bending of crustal rocks due to tectonic activity. Step 5: Comparing the options, the statement that tectonic activity breaks and bends the crustal rocks best summarises the combined brittle and ductile deformation caused by plate movements.

Verification / Alternative check:
We can verify this answer by thinking of common landforms created by tectonics. Fold mountains such as the Himalayas and the Alps are created when crustal rocks are compressed and bent into folds. Fault block mountains and rift valleys result when rocks break along faults under tension or compression. Earthquakes occur when rocks suddenly slip along fractures. None of these processes imply that tectonic forces have no effect, nor do they restrict deformation only to so called crystal rocks. Instead, they confirm that tectonics both breaks and bends crustal rocks across large regions over geological time.

Why Other Options Are Wrong:
Forms and bends only the crystal rocks: This is incorrect because the term crystal rocks is imprecise and tectonic activity affects many types of crustal rocks, not just a special crystal category.
Simply reshapes the surface without fracturing rocks: This is incorrect because fractures, faults, and cracks are very common results of tectonic stress and are essential for understanding earthquakes.
Has no significant effect on solid rocks: This is incorrect because tectonics is one of the main forces that deforms and reorganises solid rocks in the Earth crust.
Only creates new oceans without affecting continents: This is incorrect because tectonic forces also build mountains, create rifts, and deform continental crust extensively.

Common Pitfalls:
Students sometimes imagine tectonics only as slow drifting of continents and forget about intense local deformation such as folding and faulting. Another mistake is to associate tectonics only with volcanoes and ignore mechanical deformation of rocks. Some learners misread the term crustal rocks and think it applies only to special types of rock, whereas it actually means the general rock material of the Earth crust. To avoid these errors, remember that tectonic activity is a broad term that includes both brittle breaking and ductile bending of rocks under stress.

Final Answer:
Tectonic activity primarily breaks and bends the crustal rocks of the Earth.