Question

Discuss briefly how both sedimentary and igneous rocks form and discuss the likely sources of the magma that resulted in igneous rocks in Connecticut’s Central Valley.

Answer 1

Extremely common in the Earth's crust, igneous rocks are volcanic and form from molten material. They include not only lava spewed from volcanoes, but also rocks like granite, which are formed by magma that solidifies far underground.

Typically, granite makes up large parts of all the continents. The seafloor is formed of a dark lava called basalt, the most common volcanic rock. Basalt is also found in volcanic lava flows,

Granite rocks can be very old. Some granite, in Australia, is believed to be more than four billion years old, although when rocks get that old, they've been altered enough by geological forces that it's hard to classify them.

Sedimentary rocks:

are formed from eroded fragments of other rocks or even from the remains of plants or animals. The fragments accumulate in low-lying areas—lakes, oceans, and deserts—and then are compressed back into rock by the weight of overlying materials. Sandstone is formed from sand, mudstone from mud, and limestone from seashells, diatoms, or bonelike minerals precipitating out of calcium-rich water.

Fossils are most frequently found in sedimentary rock, which comes in layers, called strata.

Sources of magma:

AS PANGEA CONTINUED TO BREAK UP, SOME SMALLER RIFTS PERPENDICULAR TO THE MAIN
RIFT DID NOT OPEN COMPLETELY, PRODUCING FAILED RIFT VALLEYS LIKE CONNECTICUT’S
CENTRAL VALLEY (NEWARK TERRANE). THE FAMOUS BROWNSTONES OF CONNECTICUT ARE
MADE FROM SEDIMENTS THAT WERE DEPOSITED IN THE RIFT VALLEY. THE FLOOD BASALT
LAVAS THAT ERUPTED ALONG THE RIFTS ARE NOW PRESERVED AS TRAPROCK RIDGES. ONE
LAVA FLOW WAS ABOUT 200 METERS (OVER 600 FEET) THICK! DINOSAURS ROAMED THE
CONNECTICUT VALLEY AND LEFT FOOTPRINTS ALONG THE MUDDY MARGINS OF RIFT VALLEY
LAKES. ONE TYPE OF LARGE FOOTPRINT IS NAMED EUBRONTES AND IS THE CONNECTICUT
STATE FOSSIL.