The theory you're referring to is plate tectonics. While it doesn't specifically talk about the crust "shrinking and wrinkling," it explains how the Earth's crust moves and interacts, leading to phenomena that look like wrinkling and folding.

Here's how it works:

* Earth's crust is divided into plates: These plates are constantly moving, driven by heat from the Earth's core.

* Plate boundaries: Where these plates interact, we see different types of geological activity:

* Convergent boundaries: Plates collide, and one plate can slide beneath the other (subduction) or crumple and fold on top of the other, forming mountains. This is like wrinkling and folding of the crust.

* Divergent boundaries: Plates move apart, allowing magma to rise from the mantle and create new crust.

* Transform boundaries: Plates slide past each other, causing earthquakes.

So, while the crust isn't shrinking, the movement and interactions of the plates lead to the formation of mountains, valleys, and other geological features that can resemble wrinkling.

Key points to remember:

* Plate tectonics is the dominant theory explaining Earth's geological activity.

* Plate movement is driven by internal heat and convection currents.

* Interactions at plate boundaries create various geological features, including mountain ranges and earthquakes.

Let me know if you have any other questions about plate tectonics!