If node $2$ is midway between node $1$ and node Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "http://localhost:6011/en.wikiversity.org/v1/":): {\displaystyle 3}
,

However, if node $2$ moves away from the middle during deformation, then
$x_{,\xi }$is no longer constant and can become zero or negative.
Under such situations the rate of deformation is either infinite or the
element inverts upon itself since the isoparametric map is no longer
one-to-one.

Let us consider the case where $x_{,\xi }$ is zero. In that case,
the Jacobian becomes

This means that as node $2$ gets closer and closer to node $3$, the rate of
deformation become infinite at node $3$ and then negative.

If $x_{,\xi }=0$ at $\xi =-1$, then

$x_{2}={\cfrac {3x_{1}+x_{3}}{4}}~.$

This means that as node $2$ gets closer and closer to node $1$, the rate of
deformation becomes infinite at node $1$ and then negative.

These effects of mesh distortion can be severe in multiple dimensions. That
is the reason that linear elements are preferred in large deformation
simulations.