We model the development of turbulent patches in the ocean as due to internal wave breaking at critical layers. Numerical simulations of small-scale internal wave packets moving in a large-scale background are performed using the Eikonal technique. The wave packets are found to break in long, thin horizontal layers that resemble the turbulent patches seen in experimental records. Statistical analysis of the final positions of the wave packets yields values for typical thicknesses of between 0.75 m and 2.5 m, which agree with the predominance of the experimental data on patches. The simulation suggests that patches with thicknesses much greater than 2.5 m should be quite rare events. The statistically computed tilt of the patches from the horizontal computed from the simulation is 0.014, which is in agreement with typical aspect ratios for the background internal waves in our study and with experimental observations. We conclude that the patches created by internal wave breaking are not created as thick patches that then collapse by some mechanism into long, thin pancake shapes, but instead are created in their observed form by the very nature of the critical layer events. ¿ American Geophysical Union 1990