Metamorphic rock the foliation is called "gneissosity"), granoblastic (includes granulite, some marbles and quartzite), and hornfelsic (includes hornfels and skarn). Metamorphic rock Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure ( or more), causing profound physical or chemical change. The protolith may be a sedimentary, igneous, or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by
K-means++ the "k"-means++ initialization, the algorithm is guaranteed to find a solution that is O(log "k") competitive to the optimal "k"-means solution. To illustrate the potential of the "k"-means algorithm to perform arbitrarily poorly with respect to the objective function of minimizing the sum of squared distances of cluster points to the centroid of their assigned clusters, consider the example of four points in R that form an axis-aligned rectangle whose width is greater than its height. If "k" = 2 and the two initial cluster centers lie at the midpoints of the top and bottom line segments of the rectangle