What tectonic event caused the Taconic and Acadian orogenies? ...

[Evvie72]

What tectonic event caused the Taconic and Acadian orogenies? What will be an ideal response?

Question 2

Briefly explain the difference between the tectonic setting of shield areas during the Precambrian and
  since the onset of the Phanerozoic. What will be an ideal response?

[mochi09]

Answer to Question 1

The closing of the Iapetus Ocean began with an oceanic-continental convergent plate boundary during
the Taconic orogeny and culminated with a continental-continental convergent plate boundary during
the Acadian orogeny as Laurentia and Baltica became sutured.

Answer to Question 2

During the Precambrian, the areas that are now part of the shield were tectonically active with
volcanism, metamorphism, and folding and faulting. During that time, continents grew by accretion.
Since the beginning of the Phanerozoic, these areas have been tectonically inactive and have been
eroded to topographically flat, stable areas.

[Evvie72]

Gracias!

[Sarahjh]

Thanks for the timely response, appreciate it