To improve the cartography and depict geopolitical features as accurately as possible, Google made some significant improvements to borders for over 60 countries and regions in Google Maps and Earth. With these improvements, many borders will now more closely follow natural boundaries such as mountains and rivers. In some areas we've improved our qualitative accuracy by changing the symbology of boundary lines to reflect updated status of a treaty or agreement based on political changes, new agreements or negotiations. "Solid line" meaning "international" and dashed meaning "disputed".
Also, in other cases our previous boundaries lacked key details and the new data provides more information. For e.g., we now show a disputed island near the borders of Brazil, Uruguay and Argentina: